@biped
Thank you for your suggestions.
With regard to your first suggestion, perhaps you could use one of the following ideas.
(1)
You could use the Open Image button (set showOpenButton="TRUE" in JuiceboxBuilder-Pro's 'Customize -> Lite' section) to point to your custom pages instead of the gallery images.
By default the Open Image button on the Button Bar opens the current image's imageURL in a new tab.
However, if the current image has been given a linkURL (which you can enter in JuiceboxBuilder-Pro's 'Images' tab), the Open Image button will open the linkURL instead.
Therefore, you could enter a unique linkURL for each image (pointing towards the corresponding custom page).
The linkURL entries can be relative (to the page containing the gallery's embedding code) or absolute (in the form http://www.example.com/gallery/custom.html).
You could then change the icon for the Open Image button to something more appropriate by following the instructions here.
You could also change the rollover text associated with the button using the languageList configuration option.
(2)
An alternative solution would be to use custom purchase URLs as noted here.
(This would leave the Open Image button free for its original intended purpose.)
This functionality was designed with e-commerce in mind but essentially, if an image has been given a purchaseURL (which you would need to add manually to your gallery's XML file), then the shopping cart icon will be displayed on the Button Bar and when the shopping cart icon is clicked, the purchaseURL page is opened in a new tab.
Any image which has not been given a purchaseURL will not have the shopping cart icon displayed.
You could set the purchaseURL paths to point to your custom pages and change the shopping cart icon and rollover text as required (as noted in the links in Suggestion #1 above).
(3)
A further suggestion would be to simply include a link to each image's corresponding custom page in the image captions.
You can use HTML formatting (such as <a> tags to link to other pages or documents) in image captions by following the notes in this FAQ:
How do I add HTML formatting to image captions and titles?
I hope this helps.