it's a great awesome illustration, although as someone pointed over there, maybe the centered phone makes it a bit static. However there's some good stuff going on in the sides and maybe in other composition they would get lost, so it's cool!!
Wonderful colors used on this one, this is definetely wallpaper material.
Yet, i can see where you can make some improvements. First off, do not center the phone straight in the middle of the picture. It is kindof bland. Maybe instead you could put it to one side of the picture or put it diagonal; anything to make this even more interesting.