Thank you for removing the extra code.
It looks like your gallery is being displayed immediately below your side menu (instead of to the right of it).
Try changing:

<div id="juicebox-container"></div>

... to:

<div id="juicebox-container" style="float: right;"></div>

Hopefully this will help.

@piers.michael

The original poster's problem appeared to be due to the use of the SG CachePress plugin which was still serving Juicebox-Lite files from a Content Delivery Network even after replacing the Lite 'jbcore' folder in the 'wp-juicebox' directory with the Pro version. If you are also using this plugin, then possible solutions would be to purge the cache (by clicking the 'Purge the Cache' button on the plugin's settings page), exclude the 'wp-juicebox' directory from being cached (also on the plugin's settings page) or disable the plugin.

WP-Juicebox is compatible with Juicebox-Pro v1.4.2 and if your zip file's MD5 matches the one I posted above, then you definitely have Juicebox-Pro so the problem likely lies with either the files on your web server or with server-side caching.

The gallery whose link you posted uses Juicebox-Pro v1.4.2, displays your Flickr images and uses your Pro options so it looks like you have successfully upgraded WP-Juicebox to use your Pro files.

If you still do not see what you expect (even after clearing your browser's cache), then this leaves server-side caching as the likely cause of your problem. Please check the settings of any caching plugins you may use or try temporarily disabling them to see if this helps.

WP-Juicebox v1.4.2.1 has now been released with fixes for both the bugs mentioned above (the inability to edit galleries using WebKit browsers and NextGEN and Picasa galleries not displaying).
It can be downloaded from the plugin's own support page here.

First of all, try removing the custom CSS which sets dimensions directly on the .jcbx-glry-classic class.
Juicebox itself will not know of your custom CSS and this may complicate matters.

Also, remove the margin-bottom: 100px; CSS rule on the gallery's parent container (at least for the time being).

These may be making things more complicated than necessary.

I would then try setting the gallery's width and height to 100% (so that the gallery fills its parent container, no matter what its size) and then assign the required dimensions to the parent container.

It looks like the background you are referring to is the div with id="mainContainer" so check its height in your CSS. It looks like reducing its maximum height (via CSS max-height) may help.

If your Juicebox-Pro zip file is named 'juicebox_pro_1.4.2.zip', then it is unlikely that the files inside are Lite and not Pro.
You can check that the 'jbcore' folder is Pro by opening the 'jbcore/juicebox.js' file in a plain text editor and having a look at the comments at the top of the file.
If the 'juicebox.js' file is Pro, it will read "Juicebox-Pro 1.4.2" rather than "Juicebox-Lite 1.4.2".

The Pro Options text area is available to both Lite and Pro users (although any Pro Options entered will become active only after the plugin has been upgraded to Juicebox-Pro).

If you want to double-check that the zip file you have is, indeed, the Juicebox-Pro zip file (and that it is also complete and not corrupt), you can check the MD5 and/or SHA1 hashes of the file with a program such as HashCalc (free).

juicebox_pro_1.4.2.zip
MD5: d9b0ea9db1be174e3bea5bb678c7a003
SHA1: 0c550f7ab43fb3a2f03d53ad88a93f7fa5df6cbf

Please don't worry about using up your 5 downloads. If/when your link expires, just fill in this Download Link Request Form to request a new download link. In doing so, you will always have an active link and be able to re-download Juicebox-Pro (or download a new version when it becomes available) if necessary.

The only other reason for still seeing the branding (other than uploading Pro files to an incorrect location or uploading Lite files to the correct location) would be server-side caching, which may be serving up old (Lite) files from a cached location even after replacing the 'jbcore' folder.
Please make sure that you do not have any WordPress caching plugins installed and enabled.

Assuming you can confirm that you do have the Pro 'jbcore' folder (by checking as above), try deleting the existing 'jbcore' folder from your web server ('wp-content/plugins/wp-juicebox/jbcore'). Now, before uploading the Pro version, check your web page. The gallery should no longer display (with the 'jbcore' folder now missing). If the gallery does display, then either you are deleting a secondary 'jbcore' folder from your web server that your gallery is not using (from a location other than 'wp-content/plugins/wp-juicebox/jbcore') or there is some server-side caching happening. If this is the case and you do not have any WordPress caching plugins installed and enabled, then try contacting your web host and ask them if they have any such caching in place that might result in what you are seeing.

Hopefully this will help.

@ps76

If you ever need to edit multiple XML files again, you might like to take a look at Notepad++.
It is a free text editor which is capable of editing multiple files at once and it supports regular expressions so you could open all your gallery XML files and surround your existing captions with the <span></span> tags in a single search and replace action across all files.
Regular expressions take a bit of getting used to but they are a powerful tool when it comes to searching and replacing.

Juicebox-Pro introduced the imageHAlign and imageVAlign configuration options (to horizontally and vertically align the main images within the gallery's image area) in v1.3.0 (released on 16 April 2013).
Please see the Version History for a full list of changes between versions.
For reference, a complete list of configuration options can be found here.

If you need to upgrade you version of Juicebox-Pro to access these configuration options, please see the Upgrading Juicebox support page here.
Once you have the latest version of JuiceboxBuilder-Pro installed, imageHAlign and imageVAlign can be found in the 'Customize -> Main Image' section.

@ps76

As I am sure you are aware, when showImageNumber="TRUE", the caption wraps before it reaches the image number (so that caption will never overlap the image number) and when using captionHAlign="CENTER", the caption will be centered in the available space (which does not count the space taken up by the image number).

I understand your request (and thank you for the suggestion) but I thought that I should point out (just in case you are not aware) that it is possible to tweak the position of the images titles and captions using inline CSS via HTML formatting as documented in this FAQ. (You could perhaps use CSS margin and padding properties to shift the titles and captions slightly.)
You could maybe use a caption such as:

<caption><![CDATA[<span style="margin-left: 20px;">Caption text goes here.</span>]]></caption>

Otherwise, you could maybe just bump your caption along a bit by adding a few spaces (&nbsp;) to its beginning:

<caption><![CDATA[&nbsp;&nbsp;&nbsp;Caption text goes here.]]></caption>

I'm glad you've got it working but adding 'www' to the paths in your embedding code will mean that the gallery will now display only on www.steinjanssen.nl and not steinjanssen.nl.
Use the code from my post above (using paths with a leading slash) and your gallery will display on both www.steinjanssen.nl and steinjanssen.nl.

Please check the following:
(1) Make sure that the thumbnails have been uploaded to the correct location on your web server.
(2) Check the permissions of the thumbnail files (and their containing folder) on your web server (with an FTP program or within your web hosting CPanel) in case they are currently too restrictive and cannot be read by browsers. Default permissions of 755 for folders and 644 for files should be fine.
(3) Make sure that the 'thumbUrl' paths in the gallery's XML file are correct and that the filenames in the XML file exactly match the thumbnail image filenames themselves. Take care with uppercase vs lowercase characters. Your web server is likely to be case-sensitive and 'thumb.jpg' is not the same as 'thumb.JPG'.

Hopefully this will help.
If you continue to experience difficulties, please post the URL to your gallery's web page so that I can take a look and help further.

If the problem turns out to be directly related to the use of the Juicebox module for Drupal, then please note that we did not write the module ourselves and support for the module would be better directed towards the Drupal forum where the author of the module should be able to help you out further.

Your gallery's embedding code uses absolute paths with the steinjanssen.nl domain but the link you provided uses the www.steinjanssen.nl subdomain.
All gallery files must be on the same domain or subdomain as the HTML page containing the JavaScript embedding code due to the same-origin policy.

Use relative paths within your embedding code and your gallery should display on both steinjanssen.nl and www.steinjanssen.nl.

<script src="/gallery/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        containerId: "juicebox-container",
        baseUrl: "/gallery/",
        galleryWidth: "100%",
        galleryHeight: "100%",
        backgroundColor: "#222222"
    });
</script>

The leading slash in the paths above denotes your root directory.

It looks like there may also be a problem with the sizing of the gallery on your web page.
Please check the CSS code used to define the dimensions of the gallery's parent containers on your web page.
Alternatively, you might like to try setting your gallery's own dimensions as fixed pixel values (rather than percentages).
For example:

<script src="/gallery/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        containerId: "juicebox-container",
        baseUrl: "/gallery/",
        galleryWidth: "800",
        galleryHeight: "600",
        backgroundColor: "#222222"
    });
</script>

So the problem appears to be that audio does not play on load in the stock browser on a Samsung S3 running Android 4.3 (but that the functionality and icon status of the Audio Button is OK).

Unfortunately, this may be unavoidable (similar to iOS devices) and that the user will have to click the Audio Button to start the audio playing.

Have you tried a different browser (such as Chrome) yet to see if this makes a difference?