They make small strips of lights, like 4 or 5 LED's, run off batteries...
Assuming you don't want to have the lights on often at all, I'd go with these. You can get them at home improvement places and stuff. They're about 2 inches wide by maybe 7 or 8 inches long. You can mount them in the top of shelves and things with simple screws. They'd be my choice, ultimately.
LED's are efficient, burn relatively cool, are bright and focus light nicely.
Niub Niub used them when he did his last Celebration diorama set-up (Echo Base/Hoth) where he put them in the ceiling bits of the HOth corridors, and they lit them up eerily accurate to how the Hoth corridors looked.
If you get glass paint too, you can paint LED's other colors too, so if you wanted to have red lighting over a Sithy shelf or something, it's doable.