Dango i'm not so good @ textures but i'm now learning them. Few suggestions you could bring some blood color or some dust on his Spikes feet. You could also break up the color little but now it's just simple green you could make some dark green spots on him break up a bit the muscles make some different color onto the down side of the muscles maybe lighter green. And some other stuffs...

Just personal Opinion... Don't go onto my words if you don't find them useful.