Hi everyone! I'm new in making wallpapers,this is only my second wall. I know that I have a lot of things to edit, so If you could help me I would be very grateful :). Thanks in advance.

PD: Sorry, I'm still learning english.

There is some strange distortion on the jacket and the hair.
It is easy to get rid of that. Use the "Gaussian Blur" filter. Afterwards you can sharpen it again. (using "Sharpen Edges" twice or "Sharpen More" in PS)
Hope that helps. ^^
~TakeG

The leaves in the background is too random, maybe clutter them around Shana and just have a few elsewhere.
ps: You're english is fine to me o_o

Greetings~

Glad to see another Shana wallpaper =) Therefore, I'll try my best to help but I'll apologize at first if I unconciously use harsh words =)

Scan : Need to be extracted more. It's jagged everywhere.. Starting from her hair, I guessed you used brushes to paint her hair, didn't you? It's not quite wise that way. Try to cut out the render properly and patiently from the scan, ne?

Background : It's way to simple you have there. I suggest you not to depend too much on brushes, it won't do a good wallpaper but it doesn't mean brushes aren't helpful. Brushes're supposed to be used when it's necessary not just splash it randomly. After that, may be you should learn blendings the background and also make uses of gradients, textures and lighting effect.

I'll stop here. Hope that helps. Feel free to ask more through PM (with link, please) if you don't mind my useless suggestions =)

Good Luck~
-Breezie-

This images is can shine more with colours.
perhaps the angle of the falling maple leaves can be changed.
it seem kinda pixelated.
other than that, you got a nice impression of the wallpaper you're making...planned.