I have a space-themed game room. It has a couple of framed paintings of rocket ships, a Space Duel marquee lit by a custom lightbox, and those Space Invaders wall stickers from
Blik on the walls. There's also a shelf with a bunch of Star Wars, Voltron, and other toys on it. On the ceiling, it has a light fixture that looks like the moon, complete with little hand stenciled space men and such. The two round air conditioning duct covers have been decorated to look like flying saucers. Finally, there are little lights that kind of look like runway lights around the floor of the room.
It's still a work in progress, but it's coming together well.