Pros: Beautiful picture! Reminds me alot fo the crystal from the superman movies. blue, light blue, and white go very well together.
Cons: Interferes a bit with the menu's text. Black space in the uper corner.
Improvements: Make more use of the entire background. Try using more than one fractual image with multiple effects for a whole new image! :)
Notes: Keep making GUI's to improve. The more you make the better you will become. :)