It's a gallery/bar space, so it's always best to go simple and assume they know very little about games. Play times should be short, the games that work best are the type that you "get" in a very short time, but then can continue playing. Like say, Bennet Foddy's FLOP, it doesn't take long to go "oh I get it, it's pong but with floppy paddles", but then it's still fun to toy around with. Those work best.
Good feedback, simple to figure out which character you are or what you're doing, good for spectators as well as players, that kind of thing. Does that help?