Well, I learned quite a bit from your critique Gil, thanks!
The thing I immediately noticed was the contrast. Working with a limited palette, making those related colors pretty different goes a long way. Also, darkening the outline really made those colors pop.
After that, I had to look up what banding referred to (like I said, I've never done shading before). I saw bad banding in the left boot and in the right arm - if y'all thought it was terrible elsewhere let me know.
Speaking of things that were terrible, I hadn't noticed just how awful that lump of flesh at the end of his right arm was. Funny how shaving off his Popeye forearm by one pixel and extending the hand solved that one. I did steal Gil's skin tone and shading on the right arm because, so far, I haven't managed to find anything that looked better (if it isn't banding, it baffles me). I'm going to keep trying though - I don't want to steal from the critique.
Here's the thing I still don't get - anti-aliasing. Gil really made the hair outline flow into the guy's hair color nicely, but I'm not sure the rhyme or reason for the particular locations of lightened pixels. Is it just the sort of thing you eyeball until it looks good?
Well, enough blathering about my continued education of the pixel, here's my updated version (number 1 is the original, 2 is Gil's critique, and 3 is my update):
As awesome as the blue hue in the armor looked, I wanted to keep his colors in the "warm" range. I can't decide, though, if my choice of color has made his armor look something other than metallic.