Shading is my Problem

[Jeo]

Yeah, i have been doing customs for a month now and i have only had one major problem: Shading.

Here are some examples of my work(Latest first):
http://www.sheezyart.com/view/1789579/
http://www.sheezyart.com/view/1787402/
http://www.sheezyart.com/view/1787072/
http://www.sheezyart.com/view/1786184/
http://www.sheezyart.com/view/1783624/

Please suggest something that i can work from.

Btw, im new and wanted to know a few tips while staying here.

[TPoe]

You need a light source

[Jeo]

Is it pillow shaded?
I dont know how if it is