Clean up your lines, and it'll look much better - also... bring out your colors more and add some contrast by making your darks, darker... and your lights, lighter (Don't forget about highlights and shading). The majority of the drawing looks almost opaque, if you know what I mean.
Basically, it just doesn't look quite finished. Polish it up, and it'll be great.
I'm still new to drawing with a tablet,, and as for the coloring,,, I still don't know what I'm doing. sweatdrop I'm trying to teach myself how the art program I'm using works. I'm such a noob at this..... gonk