Ok, back to the Mario idea. If you had a Coin Box lamp, you could make coins, the cord goes up through the coins and holds the coins above the lamp. It would look like they are flying out of the lamp.
Donkey Kong girders could also be used as shelves on the wall. Make some barrels to place on there for show or to put stuff in. Your wife will put flowers....
You could make a pretty cool Pacman maze shelf as well making it look like a section of the maze.
A Pacman or ghost Lamp would be cool, on a desk or hanging would be ok.
Could you make a Tempest board on the ceiling with EL wire? It would make a great night light.
If you can get a cylindrical hamper you could paint or cover it with cloth to make lots of game characters. Pac ghost would probably look pretty good. Or the cylinider you have the shoot your way up through in Tron.
Oh, Joust shelves would be cool too. Especially if you could get a model of an ostritch and stick an action figure on there.
The Defender aliens would make a good lamp too.
If you can buy the characters, probably from keychains or something, try to make an arcade mobile for the crib.
Pull the current switch plate off and redecorate it arcade style. You can get some Super Sculey clay to make a competely new one. Then paint as needed. That stuff is cool.
Or, if you want to try and figure it out, make the light switch an arcade button (a player 1 button). There might be some safety hazards there though.
Cheesey, but maybe you can put marquee graphics on the front panel of the drawers. That might look ugly?
You can run a cord from wall to wall with a little guy haning on it, if you like Elevator Action that is.
If you have a window, make one of the Rampage creatures look like he is hanging on the top corner of it. As if the window is a building.
As for the walls, print out characters from games and laminate them, YOu might try to set up a level of Galaga on one wall, Frogger on another, Donkey Kong on another.... I wouldn't try to collage a bunch of characters all over, it may just be messy. Although, I'm sure I could be proven wrong here. If you placed them in a logical order interacting on the wall it would work. Especially if you made some 3D stuff to hang with it.
You could really score big if you can sew (I can't). There are all kinds of pillows, bed runners, bumpers, blankets, diaper holder, wipey dispenser that could be made if you know what you're doing.
I would make some kind of border, preferably a retro style border. Then place all off the decor above it. Try to leave the bottom half of the room simple.
Alrighty then, back to work....