It seems to me that you're forcing yourself to use 3 shades of any one colour at a time. Why? Quite alot of the time you only need 2, perhaps even 1, and yet you force another in there. Remember, if a colour isn't needed, then it isn't needed.

I think your monster (in fact, both pieces) are too small to be including black outlines. And your colours have incredibly high saturation, which makes them quite hard to look at and enjoy atall. I'd avoid using MSPaint default colours whenever you can. You can make a new colour very easily on paint, with much freedom, and to save it just place it near your image so you can pick it up later (seeing as the recent MSPaint won't allow saving palettes..)

Hope that helps...