I learned about this collaboration today through deviantart, and thought it sounded interesting.
You can create a tile that will be part of a huge collaborative art project about the world we live in. In addition, the "fee" to sign up is simply a donation to a global humanitarian or environmental charity - the group running the project hopes to raise $6.5 million for the several causes it's affiliated with. So check it out, enjoy the artwork that people have created, and think about making a tile yourself! If you do make a tile, post a comment here with a link to it, so that I can check it out!