For lighting, if you go with red LEDs, you won't need much battery power at all. Most red LEDS operate off 2.4-2.7 volts, even the very bright ones now available (about 20,000mcd brightness, if I recall rightly), and with a very low current consumption. Two rechargeable AA or AAA batteries give you around 2.4 volts. I made up a couple of redlight torches, following the description here:-
http://www.iceinspace.com.au/index.p...63,278,0,0,1,0
They use 6,000mcd LEDs. I used rechargeable AA batteries - NiCds or Lithium, I cannot remember - and thought I'd better check how long they last. Well I left those two torches on in my house for 20 hours before they started to dim!!
So using a red LED, you'll need batteries, battery holder, wire, switch and LED - nothing more sophisticated - arranging mounting it all will be the biggest problem.
I wouldn't worry about dimmers - just have several LEDs that you can switch on separately - all on for bright, only one on for low light??