Edit: Thanks Emperor for the feedback. I agree with you, so I'm going to re-do them. Will make a new thread after, requesting lock on this one.
It's ugly, like very ugly. It's really plain, the colors are bland and uninteresting. It looks really flat and not very sleek. Like you should add some depth to it and pick better colors for the default. Then on the nebula one if the header is going to be really dark then the rest should be or at least a color that isn't going to directly contrast so much. Also more subtle gradients, better nav bar, and 2 px borders.
That is just my opinion though

