I think they're all pretty sweet! Now, the following is simply an opinion, so take it for what it's worth! Overall, I really like them all. There are only a couple of minor changes I would suggest... For the first two, I would try and let the stars show through in the black areas around the top alien. I think that would make it more seamless, and may improve your liking of it. I would also think about softening the transition between the bottom background and the stars above it. The right side of it looks like it's already softened, but the left side is a hard transition.