As a painting contractor myself, I'm glad you are painting the ceilings white. Your ceilings are too low to paint black. If anyone is claustrophobic, they wouldn't be able to go down there IMHO.
I like the dark purple for some walls. You could break it up with a dark gray or dark maroon. OR you could go dark purple with some bright neon colors as well. Don't just go all 1 color if you don't have to. Multiple colors will give the room more life, feel and depth.
You should have them put in a recessed trim moulding around the entire downstairs wall perimeter. Then have the electrician wire up some RGB led lights on top of the moulding and all the way around. That will really make the room pop for you.
You could also add a couple of floor to ceiling mirrors around the room to add some additional depth if you feel it needs it.
Another great addition is the glow carpeting. I know you said you were lazy, but that dark carpet hides the dirt well. A quick once a week 20 minute vacuum is all you need. The carpet not only looks nice and neon colorful, but it also helps to insulate the floor to keep the room warmer, deadin the sound which will make everything sound better (it will eliminate echoing) and it also gives nice cushioning when walking around down there in your bare feet.
Also, now is the time to have the electricians pull wires for you big screen TV and surround system. Get those wires behind the walls, not out in the open where everyone can see them. Do it NOW while the walls are opened up and the electricians are there. You'll regret you didn't do it later. Of course that's if you plan on having that down there.
These are all various things I have seen done in some very expensive homes. They looked awesome. Wish I had pics.
Anyway, no matter what you choose, I wish you the best of luck bro. It's gonna look awesome when it's done. Congrats on the new home and the new arcade.