LED bulbs can be used for Space Buckets, and they are a good replacement for standard CFL builds. The main advantage of LED bulbs is that you can keep the heatsink on the outside, avoiding many heat problems. They also have better electrical efficiency and are commonly cheaper than equivalent CFL bulbs. For better results, you can to remove the protective cap on top of the bulb to take advantage of LEDs unidirectional light output, as the cap will diffuse the light in different directions. Make sure the LEDs are all pointing the same way. This will optimize the lighting configuration.