The beard isn't reading well, looks like something over his shoulder. Hm.. I can't explain the problems as well as show them, so here's a quick edit:
-Changed the pose to look more relaxed and/or realistic
-Raised the belt to give him a waist area
-Shrunk the arms/fists to look more natural
-Shifted the beard to be under his chin
-Removed redundant skin color
I'm not sure what's going on with the hat-thing, so I didn't really do anything there. Same with the necklace (?). I tried to remove some of the harsher outlines from his expression as well.
Now I know there are numerous problems with my edit as well, but hopefully this can start you off in the right direction.