It is really easy, actually. You just use Apophysis. I haven't even read any tutorials or anything--I don't know much about the program--, I just mess around with the parameters. Every time you run it, it generates several images that you can use as bases.
RonFrank, those are great! You really should get back into drawing again, you do have quite a talent there. I quit drawing in 10th grade too, and I'm just getting back into it again this year. I have yet to finish a full drawing though.