Wow! Nice Wallpaper! What did you use to make this? (if you don't wanna answer then that's perfectly fine.)
I've used Photoshop CS6 :3
I like everything about this wallpaper except the light sparkles. They feel too... Superficial? Amateur? MS Paint-ish? I think a softer glow or sparkle without the lines would have been better, or maybe place them behind a few layers to give a grid effect in the background instead of putting it in the front which mates it feel a little too busy. Just a little bit of constructive criticism. Really great Job on everything else. I like the way you used the apple shapes in the background. Nice choice of fonts.
I've never seen this character before. Is she a background pony?