Try lots of little spheres set to the size and position you want(I hope thats not as bad as lots of little lights) texture set to Fuzzy, and ambience and diffusion set to the colour you want, and both set to 100%, turn off cast shadows, self shadows and receive shadows, turn your sky to night, but keep your sky ambeint colour white...I just tested this idea as I was writing this,(I was curious myself) and it took approximately 15-20 seconds to render...with about 30 little spheres, and no other objects, using Bryce's default sky set to "nightime" here is a picture...hope this helps :) PS: my computer has 64 meg of ram, and is, generally, very out of date, (about 4-5 years out of date, as far as the motherboard, ram and processor is concerned) so this would be even faster on newer machines/processors ect.