I have used lightstrips from SuperBright LED's. They are similar to ones posted above but come in shorter sections. They can be cut in 3 LEd segments about 2 inches IIRC. They work on 12 volts, have the resistor included and even a plug that can be used. The problems are two fold. First LED's are not "white" they are ultraviolet with doping to make them appear white, therefore the color rendition may not be as accurate as you would like. Second, they are ugly, you will have to build some sort of frame, cover etc to hide them. The light is emitted in a downward direction so the frame will have to extend far enough to the house the lights and allow the light to reach the entire picture. These lights are surprisingly bright and depending on the pictures finish, may actually reflect the individual bulbs. In closing this may work. LED's have many advantages, but they are not a panacea. The good ole incandescent, with all their drawbacks are still the best bet for many applications, this is one of them.