how would the social aspect work if the project description is private?

Sounds interesting. High scores could be problematic for arbitrary-sized fields though. My idea would be - do proper user-profile coding, then allow users to upload any number (up to a reasonable number) of images to define their playing field and then distribute links to their custom memory game they "created" - that way each field would be unique and can keep individual scores (different images and field sizes have different game complexity).

And solves the "look for nice images" part, too.

I am finishing one hobby project this weekend but starting next week we can do this. You thinking Google Apps or self-hosted?