Well, we did it.
We converted our garage into a game room/teenage hangout for A and her friends. Christopher and I have been using it just as much though. :)
It's nothing to fancy, it is after all, a garage. There are a few shelves that still have "garage stuff" on them, but I covered the from of the shelves with colorful beach towels so it looks better. We still need to get a carpet and a few posters for the walls, but it is usable now as it is.
The room has a nice dartboard, a ping pong table, some chairs, a card table, a stereo and some board games. It's not much, but we all like it.