http://www.freewebs.com/sweetyella_4_ever/animegirl.htm
If you don't like the background I could just leave it all black. If you want!

Well, here's my two cents. The scan looks really bad quality. You can see grainy spots on her neck, face, hand, and hair. Some of the edges, noting the one outlining her face, eyes, and hand, doesn't look all that smooth. You can fix the edges by taking the pen tool and outline those lines, making it smoother again. I don't mind the background, it just seems a bit too simple.

Well, the first problem is the fact you don't have photoshop.
if you did, the problems would be A LOT easier to fix.
basically to start...the MAIN problem is how low quality is.
the concept itself isn't bad, but it's extremely dark. if aoi was her original color, and the background was selected to match the color of her kimono or hair, and those dots were added, it would be far more appealing.
also, some kind of simple design added to the back as well might help spice it up a bit.
it could use some work, but it'll need to be done in steps. first step is fixing up the quality of the image, and bringing it's colors back.

If you don't want a busy background, all you need to apply is a nice gradient from deep hues of something like cherry pink and purple. Add some almost-white petals falling and hey, instant simple Aoi wall :P

Don't shout in thread titles.

A grainey, jpeg artifact riddled, picture of a girl on a black background is, to me, not what I'd call a proper wallpaper. It's the sort of thing you do when you need a break from proper walls :/.