5min edit:


The piece is looking good -- still needs some work, though. Two problems I notice mainly are some weak color choices and quite a bit of banding. I did a quick stab at some possibly better colors -- mainly, I increased the brightness and shifted hues between colors on the ramp. I gave the sword-thing a bit of a hue shift as well, which might have been overdone, but goes to show that some shifting makes metal objects a bit more interesting and warm/cold (depending on what colors used -- this looks warm because I used more warm colors). As for the banding, I didn't get to fix much, but the selective outlining on the arms isn't working out so well, and internally there are a lot of "fat pixel" bandings -- not so many staircases along the borders, so nice job there. Two main areas of concern are the head and the hair, which have the most banding. I also think the face could stand out more (maybe more pronounced facial features, like bright eyes?)
EDIT:


Made a few extra quick edits. Started mending some of the banding to show a few possible fixes for that. Did a quick redo of the hair -- the way you shaded it made it rather flat. Fixed some of the AA and selective outlining (I assume that's the thing you were going for, so I made it use that more consistently throughout.) Red's face looked weird, and I figured out why -- the eye furthest from us looks a bit out of perspective from the rest of the face; however, I could be wrong, so I just made that edit so you can decide.
I'd also suggest dropping your color count, you have a few colors that can be merged -- you're at 29 colors now, you can drop to 24 with no differences to really be seen. In fact, you could even drop down to 16, and it looks good:

