Well, I would recommend a softer green shade instead of the red, which will still highlight the bored and show the text well enough. I would also recommend sizing down the ship to fit within the signature.
However, apart from those two things, it is all good.:)
Ok:
1. Change the Red.
2. You might want to try PhotoScape, it is free and very easy to use.
3. Does Gimp/What ever your using have bloom? If so, use the Deep mode on it.