The demos on this page show what can be done with Juicebox but the themes are not downloadable.
A Theme Gallery is planned but not yet available. Please see the Juicebox - Theming page for more details.

Which theme did he pick out? We only show 1 example of a custom theme. All of the other demos are achievable via the config options.

The paragraph of information below the image is actually not part of the gallery but simply part of the web page that the gallery has been embedded into.

However, you can have your captions displayed below the main image (but still within the boundaries of the gallery) by setting captionPosition="BELOW_IMAGE" in your gallery's XML file.
If using JuiceboxBuilder-Pro to create or edit your gallery, the 'Caption Position' option can be found in the 'Customize -> Caption' section.
Each image can have its own caption (entered into the 'Caption' text field on the 'Images' tab) and you can have multi-line captions by using HTML line breaks ('<br>'), e.g.:

Line 1<br>Line 2<br>Line 3

It is also possible to display captions outside the gallery in another <div> on your web page by using the Juicebox-Pro API and specifically the getImageInfo() method to retrieve the caption of the current image to be used elsewhere on your web page.