Ok, I just had to share this video I stumbled across on an amazing way of making a regular 2D jpeg image look like its moving in 3D space :O He shows it being used on more than just clouds as well.
http://www.youtube.com/watch?feature=player_embedded&v=lMKuHILi0Ho#!
http://www.youtube.com/watch?feature=player_embedded&v=lMKuHILi0Ho#!