not a bad start. Heres some basic observations:
check here for some more info on banding:
http://www.pixeljoint.com/forum/forum_posts.asp?TID=11299as far as I understand, selout is just AAing into a background when you dont have a consistant background (the background is transparant, it is a game sprite etc). Selout is generally considered to be a bad practice. AAing into a background on the other hand is fine, provided the background is consistant.
On the last image, without outlines, heres some basic observations:
1. Consider contrast and saturation. High saturated colors can look too similar within a given value range. High saturated blue and red are notorius for this. See youre hat doesnt have enough contrast.
Also consider: Does everything have to be saturated? Also should the light areas and shadow areas both be highly saturated? Try to create a light logic (more saturated lights, lower saturated shadows, or vice versa).
2. Color ramps and hue shifting. For example greens could become more yellowish in the lights and more blue in the shadows, rather than being the same hue at every value. Warmer lights and cooler shadows is the norm, but it isnt an unbreakable rule.