Wowsers Batman! That's CRAZEE!!! Done in MSPaint?!?! gaah! *bows* totally ama-zing! Truly honestly!!!
As for shading, you might want to use more of a contrast in your choice of base and shadow colours. I notice you've got very subtle shading there. It actually goes really well with the whole pic, but if you aren't satisfied, maybe try going darker for the shadow. Also, try and visualize a lightbulb postitioned around the character. ...OR even lightly sketch it on the actual picture so you don't forget where it was. The best advice for shading is by observation though. Look at pictures in magazines or books, or even get a patient friend to sit infront of you!
Blegh, I hope I helped! I might have started rambling somewhere in there... ehhe!
Post more of your art! Now!!
