The lighting on this piece is great. I love how blue light is hitting from the right and a warmer light from the left. Sorta like moonlight vs firelight. I don't see any problems that weren't already pointed out.
Also, since it looks like your going for a relatively realistic image, your mace doesn't need to be that big to kill someone. I would be impossible to lift and would just weigh you down. Make it about half that size and you've got a badass weapon.