Who? When? Where?
A variation of "20 questions" where you take submission photos with a description of who it is, and when and where the photo was taken. Then you post the photo and let people ask yes or no questions until they figure out who the photo is, and when and where it was taken. The first person to get all three correct is the winner, but they only have until the post pays out. If no one gets all three by pay out, the person who submitted the photo is the winner.