If you don't mind the fact that it will blow your usb bus and ipac, go right ahead!
You can get a cheap $1 1 or 2 light fixture and use CFL bulbs. I have seen that setup in 2 of my games, and it works wonderfully. You can also buy an $8 18" flourescent light assembly from Wally-world.
Personally, I don't use the CPU power supply to power anything not directly tied to the computer. No point in the risk to the most expensive component in the cabinet.