I've recently stumbled on old mongocosm, somewhere in synergy archives, and I found it cool and it inspired me
It would be a cool synergy project to have like, an image with caption text, and hotlinks in the caption text that would lead to more images. Hotlinks would start linking to a "add you piece" page, and people could add their own piece to create some kind of big twisted collaborative narrative with image.
There could also be ways to link back to an existing image
Now, I don't really know how a Synergy project starts, and there might not have been a new synergy project since like 10 years, but I think it would be a really cool project, and I would totally be willing to help putting it in place.