I love a good necromancer now and then. I think your facial detailing and armour/outfit detail is good. I do like the facial expression being given off here using just the facemask and the weapon is a nice match to the mask. I love your detailing inside the armour with the finer details and colors here and there. I do think the background of pure black is fine but you could add some stars in there or a mystic spell mist of some sorts. The halo could use a big burst of glow effects to really bring that out and that would work well with a background or a spell.
~~THINGS TO IMPROVE ON~~
This really just needs a background because everything else is great