Amy and I had a lot of trouble coming up with wedding/reception themes. We thought about doing an around the world theme, with each table being a different country. This isn't because we're well traveled, but because we could use it as an excuse to have a wide variety of ethnic appetizers, dishes, and deserts. We quickly gave up on it and went generic. It was just too much effort.
These people went with a video game theme and it seems to work for them in a very nerdy way. I wonder if you can tell the age of the guest by the table they're seated at. If the parents are at Pac-man, do the grandparents wind up at Pong?