It's very simple: someone posts a screenshot from video game, and everyone else are trying to guess it. After the game is guessed, the person who was right can post another screenshot. You can post AAA games and less popular Indie games. If there is no progress, posting hints is allowed. After 24 hours without new riddle from the winner of previous one, you are free to post next screenshot - this will prevent us from stopping game for longer time
UPDATE: Just want to state obvious: but if no one can guess a screenshot, the reward goes to the person who posted it.
I will start with this one: