I think that its awsome... My favorite pic of vegeta, the "pain" one ,is in there and that makes me like it even more, i think if you tried to put something in the background it would only take away from the 7 different parts and would not be as affective, i like them seperate and in the different colors just as you have them now. Good Job!
(One Question, where is that pic from the top left from? I do not recognize it)