It's a bit, um, busy. I can't really tell what's in the picture. It's nice, but all the shiny stuff kinda drowns out the main focus of the banner. Your big Friend Code thing is kind of glaring, too. So, 6/10.
And please be nice! This theme is the first thing I ever made on Gimp, and I know it's pretty substandard. I'm working on a better one right now!