Edit; Well, I had a slow morning so I updated this. Enjoy.
Here?s a topic where I can put in some generic links regarding 2d art, skins, textures, the works. Others can add if they find something useful, or ask, because I can probably throw an answer or help you out.
GENERIC RESOURCES
http://www.cgtextures.com - Free, Hi-Res pictures of materials.
http://www.brusheezy.com/brushes - Photoshop brushes and patterns
http://www.dafont.com/ - Free custom fonts
http://www.photoshopstar.com - Photoshop tricks and tutorials
http://www.tutorialized.com - PSP and Photoshop tutorials
http://www.planetphotoshop.com - More generic tutorials and tips
THE ULTIMATE BASICS
Paint and use layers instead of everything into a single layer. Layers explained
Dodge and Burn are good for painting light and shadows. Some explaining
Here is a few .pdf files that explain general texturing and 2d art, how it works, what to keep in mind, etc. Just theory
Also, work on higher resolution than the final size, because its alot easier to paint the details in and things like that. It forgives alot more.
TUTORIALS
This is quite heavy on dodge and burn basics.
Plenty of tutorials and stuff regarding clothes and flesh. Good stuff.
Huge list of things regarding everything from modelling basics to skinning to animating. They?re categorized in topics, so scroll down for the skin stuff.