If you drew that,you have some talent. just try practice some more okay? ^^ oh by the way,nice colouring ^_^
Suggestion: Find the burn tool and work with that, it takes a while to get used to it, but it is used to shade and shadow parts of the image, keep it around 50% and just experiment with it. Also use the Blur, Smudge, and Sharpen Brush, they are a little odd to learn but it will give the pic more depth instead of flat looking. Just keep working at it, you will get it.
I don't think the blur and smudge are to much to worry about, I think mostly adding depth with the burn tool will help alot though, and you just need to play with the strength of it to see what works.