The outline is a bit bright, trace over the light bits with the darkest colord take the color of the main color, set the transparency to about %50 and outline what you just traced over. Other then that, these are really good, the facial exressions are fantastic.
They still seem too dark and a bit too saturated to me. But then most of my stuff ends up being desaturated and low contrast, so...
I think your greens need to be lighter. The expressions sort of get lost on the dark colors.
Smileys own :3!