Just a few things. First off, don't stretch stuff out of their original proportions. (In this case, the sun.) Makes 'em look weird at best, mostly. If you want to keep the original proportions when you resize an image, hold the shift key while shrinking or enlarging it. If you're still using Gimp, though, I can't help out with how to give it some lighting.
Anyway, I think a ship would fill it in nicely. You could also add some text, like maybe the name of the ship/character? Dunno.
THEY TOLD ME I COULD BE ANYTHING SO I BECAME A SIGNATURE PLS HLP