actually is one of the best I have seen for firsts. To keep the theme going, all I suggest is tone the colors down and take the background away so its transparent.
It's simple. I don't consider this a sig but more of a banner.
I think it's too big. The smaller it is, the easier it is to work with. It just means less space for effects which leads to less mistakes.
Some of the brushes are cut off which isn't your fault but more of the person who made the brushes.