I'll second the LED light strips. Many ebay vendors sell the LED 5 meter reels along with a wall wart of the correct voltage to go with the reel. You can get the 300 LED or 600 LED reels, depending on light requirements, many choices out there. The dimmer modules TedW posted above also look nice, I may have to get some of those myself.
I put a 5M reel of bright white, 600 LEDs under my layout so I could see better and find things I have stashed down there. I bought 2 reels for the project, but decided one was plenty after getting it strung up. I used only the sticky backing on the reels to secure them and they have been up there for 3 or 4 years now with no sagging or loose spots.
I think the 300 LED reels need about a 2 amp regulated power supply. So I guess the 600 LED reels would need about double that. I believe I got a 5 amp wall wart for my two reels, but as said above it's now only powering one reel.
Here are some pics from my phone. Not the greatest and I know you will have less vertical space, but it may give you an idea of what they might look like.