It looks like that, for what you're achieving, you're using way too many colors. About half of them, without being generous, are wasted, as they're only slightly different in both hue and value (mostly dark greys).
If I pick up Photoshop and try to save that as a PNG8 image, then try to reduce it from the current 144 colors to 80, I can't really spot any really noticeable differences. That could be further reduced to about 30 and there would still be very little change.

Part of the beauty, for me anyway, of working with pixel art is working within limits of both size and color. But by reducing your palette you would (most likely?) also unify the whole picture.

As for how the image reads... I can tell what it is, and what he's doing... But like SeinRuhe said above, your anatomy could be improved.
His left arm (the one holding the piece of meat) hardly looks like it's his own. His right arm isn't too bad, but it doesn't read as being bent at the elbow.
You could try and draw it as a larger piece starting from a very basic skeleton, then building it up with spheres and cylinders now that you have your main idea down, just to give it more structure and volume. Try not to intersect anything with anything else, but rather only compress the softer bits if needed.

cels also gave good advice on how the halo and the gun should help light the figure. As they don't impact the figure in any way, they look like an afterthought. As you decided to put them there after you shaded the rest of the piece.

Overall I think it has a lot of potential, and the character itself is pretty cool, so keep it up!

-----

EDIT:

Please excuse that quick, dirty, and not that pixelartsy job.



-----

Would be interesting to see bits of where the jacket ends too:



-----

EDIT2: Actually, I think his right arm is fine as it is. Mine made his shoulder become toooo wide.
(always remember to flip your artwork to check for problems in all sorts of things, including symmetry.)



I moved the shoulder to the right a bit (our right).

while i am loving the angle on this dude, it's a bit hard for me to parse anything below the neck on this fella. Something's up with the clarity there!