KIM! I figured out how to make the gallery block thumbnails clickable: when you click "edit" for the gallery, there are two tabs, one for content and one for design. In design, I set the aspect ratio as cropped square, which I think looks nicer than the mixed aspect ratio grid in the original gallery block. Then I clicked to ENABLE LIGHTBOX. Now they're clickable! More options to consider for displaying PROJECTS, or sets of images within your main categories.

The gallery block below is a "SUMMARY" gallery block.