The rainbow stuff itself looks really good, but i dont think it fits good with the rest of the stuff, it just contrasts too much. I think it would look really cool if you painted over the rainbow with black and put like stars or planets and such on it. Or do some type of gradient so it fades from the color of one painting to the color of the other.

EDIT: Sorry if i sound like a dick, i think that your paintings are amazing, but i just wanted to give me 2 cents.