CMS collection lightbox, showcasing multiple projects

I need some help with lightboxes. I would like each service i.e extensions to have a grid of projects at the bottom.

This lighbox grid should show one image from each project within the CMS collection and then scroll through the remaining 24 images from that project.

Ideally I will fill out one form in the CMS collection to do the home page as it is now and then the gallery on that service page.

Here is a link to the site if you want to have a look.

Any help would be greatly appreciated