I had an idea for a long-term, online, massively collaborative game like this years ago, but had no idea how to make it. Perhaps someone else can.

Turn a picture like this into a jigsaw puzzle, and then let people place the pictures. At the start of the game only release a few pieces. As pieces are placed correctly together, spawn new pieces that fit, somewhere, on the border of the part of the puzzle already completed. As the puzzle grows, players can zoom out (like the linked artwork).

Let many, many people work on the same puzzle and maybe have an ongoing chat for collaboration "let's all work on the part in quadrant 23 (or something).