The easiest way to fix it (outside of using a filter like I did) is to pick a really dark color and go over your shadows with it, and use a really bright color and go over your highlights. It's tough to avoid ending up with a flat image, but it really pays off in a big way to pay attention while you're working to how dark or bright your darkest and lightest areas are. Just try to keep it in mind.
Regardless, it's a pretty solid piece! The finer details are a bit messy, but the metallic sheen on the myr is aces and the image as a whole works really well.
If you want the specifics for how I adjusted it:
I just copied it so I had two identical layers. I bumped the contrast up on the top layer, and then erased out the background with a soft brush, leaving only the foreground on the "high contrast" layer. It's a quick fix, but I'm a big fan of picking the right colors from the get-go, since in the long run it'll help a lot more.