I like r4c7's use of purple.

But I don't like the dark edge you guys have for the cave walls. They make the cave walls look like bushes or trees, instead of rocks that are rising out of the muddy ground. Also, things that are closer to the viewer, i.e. higher up, should be brighter. So the top of the walls should be brighter. Assuming everything is the same material, the cave floor would be the darkest and the tallest parts of the cave walls would be the brightest.

It looks kind of like you started with a dark outline and worked from there. Maybe you would have more success if you focused on the shapes rather than the lines, and really studied where the reference sketch is lighter vs darker, instead of adding highlights to fit your dark outlines.

I'm just making assumptions about your work process here, so maybe I'm way off.

Also, I would say that the challenge with the DB16 palette is to use many different colours to make up for the lack of colours. For example, there is no red, so you need to use a mix of brown, pink, orange and yellow to create red objects. In this case, I would look at alternatives to just using the grey colours.

Here's my humble edit. I'm not great at pixel placement at this scale, there may be some issues with banding.

This looks brilliant already. The little feather / ear bounce is particularly charming.

I'm no expert on anatomy, but it seems to me that his left leg is pointing so much to our right that it would be impossible for him to bend the knee without moving his knee forward. But maybe the slight bounce is not enough to warrant the knee moving a full pixel to the right, I don't know.

I don't know how people tend to do idle animations, but my impression is that they're meant to look like heavy breathing and/or idle movements like stretching, flexing, etc. This guy seems to have a lot of vertical movement from the bending of the knees, while his arms are completely locked and are barely moving independently of his torso. It actually makes him look a bit like a boxer, who's keeping his arms tight on purpose (as a guard), while bouncing up and down. But then, you would expect him to stand on the balls of his feet. If this is for a game that is primarily about running and jumping instead of fighting, then perhaps you could loosen up his arm, shoulders and torso, like he's taking deep breaths. Hell, even in Street Fighter 2, many characters look like they're taking very deep breaths when idle.

In regards to the running animation, I don't quite understand what you want to know. Are you simply not sure how to start drawing a basic running animation? If that's the case, then just googling running animation is always a good first step. Beyond that, I'll leave any elaborate explanation to more educated artists. I've seen a lot of people say that it's very hard to do a nice running animation with only 4 frames though, so you may want to reconsider and go with 6 or 8.

Hope this helps, even though I don't really know much about animation. People with more knowledge will come along shortly, I'm sure.

I was going to do an edit, but I probably can't do a better job than Manupix

Nope, you probably can't.

Reverse psychology, see? 

@Manupix, that edit was extremely helpful. It'll take me a while to fix the issues you've worked with, but I'll get it done. I feel like I see the light in the end of the tunnel now, thanks.

@Fizzick, thanks, I'll have a look at the right hand.

UPDATE:



Still not done resolving all the issues that Manupix adressed, but I'm getting there. Changed the tassles from green to blue. They're supposed to be blue, but I thought green would give better contrast, and now I've gone back to blue. Do the colours work? I think so.