The Facebook thumbnail functionality should be working fine in the current version of Juicebox-Pro (v1.5.1) as demonstrated in this sample gallery.

It should be noted that it is not possible to have the shared image's thumbnail displayed in the pop-up Facebook share window due to limitations imposed by Facebook on what data can be passed via their share URL. Only one thumbnail image can be used per web page. However, the shared link will still point towards the correct image within your gallery.

Facebook uses the data from Open Graph meta tags to populate the share window.

The thumbnail image displayed in the Facebook share window is determined by the og:image tag.
This specified image is displayed when any image in your gallery is shared.
You can think of the og:image as being representative of the gallery as a whole so you could use an image which best represents your gallery. (The og:image does not need to be an image from the gallery itself.)

When you create a Juicebox-Pro gallery with JuiceboxBuilder-Pro, Open Graph tags are included in the gallery's 'index.html' file (and the first image in the gallery is used as the og:image Facebook thumbnail).
The tags will looks something like this.

<!-- START OPEN GRAPH TAGS-->
<meta property="og:title" content="This is the Gallery Title." />
<meta property="og:type" content="website" />
<meta property="og:url" content="http://www.example.com" />
<meta property="og:image" content="http://www.example.com/images/IMG_0001.jpg" />
<meta property="og:description" content="This is the Gallery Description." />
<!-- END OPEN GRAPH TAGS-->

og:title uses the Gallery Title ('Customize -> Lite').
og:url uses the Share Url ('Customize -> Sharing').
og:image uses the Share Url and appends the relative path to the first image in the gallery.
og:description uses the Gallery Description ('Customize -> General').

If you embed your gallery into a custom web page (and do not use the 'index.html' file generated by JuiceboxBuilder-Pro), then you'll need to manually add an og:image meta tag to your web page. Please make sure that the content is in the form of an absolute URL (such as http://www/example.com/images/image.jpg) and not a relative URL.

If, after adding an og:image meta tag to your web page, you do not see the specified image displayed in the Facebook share window, then you might need to use one or more of the following online tools that Facebook provides.

(1) Facebook's Sharing Debugger: https://developers.facebook.com/tools/debug/sharing/
(2) Facebook's Batch Invalidator: https://developers.facebook.com/tools/d … ing/batch/
(3) Facebook's Open Graph Object Debugger: https://developers.facebook.com/tools/debug/og/object/
(Click the 'Fetch new scrape information' button.)

Running your web page's URL through these online tools should clear Facebook's cache of your web pages and fetch new scrape information from your gallery's web page.

Note for WordPress users
In a WordPress environment, the easiest way to include Open Graph meta tags in all your WordPress web pages is to use a third-party plugin such as the WP Facebook Open Graph protocol plugin.
Once activated, go to 'Settings -> Facebook OGP' (from the WordPress Dashboard), enter your 'Facebook User Account ID' and the URL of the image you want to use as the og:image in the 'Default Image URL to use' text field and select the 'Force Fallback Image as Default' checkbox (to ensure that this image is always used).
This is just a suggestion rather than a recommendation. Other plugins are available. Try a WordPress plugin search for terms such as "Facebook Open Graph meta".

I hope this helps.
However, if you continue to experience difficulties, please try to explain your problem in greater detail (I cannot be sure exactly what the problem is that you have encountered) and I'll hopefully be able to help further.
Thank you.

The Juicebox skin for jAlbum does generate Open Graph tags but because the og:image entry must be an absolute path and the skin does not know where your album will be uploaded to on your web server (there is no shareUrl input field in the skin like there is in JuiceboxBuilder-Pro), the skin cannot auto-fill the og:image tag with a value.

After creating an album with the skin, just open the album's 'index.html' file (in the root output directory) in a plain text editor and change:

<meta property="og:image" content="" />

... to something like:

<meta property="og:image" content="http://www.example.com/images/image_0001.jpg" />

Please note that an album created by Juicebox skin for jAlbum displays all galleries from a single HTML web page (the 'index.html' file in the root output directory) switching between galleries using JavaScript and so all galleries will share the same og:image.

If you are looking for an automated solution to creating and listing multiple galleries, then you might be interested in another one of our products, namely Showkase.

Showkase is a PHP web application (installed on your web server instead of your computer) which allows you to create a complete portfolio web site (integrating multiple galleries) online.
Showkase has full support for Juicebox-Pro and the galleries can be created within the application itself in a web browser interface (or created with JuiceboxBuilder and imported).
Each gallery has its own individual web page so each gallery will have its own og:image tag.

You can create Gallery Index pages and have as many galleries listed on each Gallery Index page as you wish.
Each gallery is represented by a thumbnail image with the gallery title displayed below and the gallery is opened when the user clicks on the image.
Demo sites created with Showkase can be found here and a sample Gallery Index page can be found here.

Showkase can also create non-gallery pages (About, Basic and Contact pages) where you can add information about yourself (or any other content you like).
All of this is done automatically within the Showkase interface without the need for any manual coding at all.

Showkase can be purchased as Showkase-Standard (which comes with Juicebox-Lite, the free version) or Showkase-Pro (which comes with Juicebox-Pro).
The only difference between Showkase-Standard and Showkase-Pro is the bundled viewer (Juicebox-Lite vs Juicebox-Pro).

As you already have Juicebox-Pro, then you could purchase Showkase-Standard (if you wanted to) and integrate your Juicebox-Pro files by following the Installing a Pro Viewer instructions.

I hope my notes above help.