Valve has tendency to not accept submissions with skulls or gore since they cant be used on the chinese client. Im not sure if it affects you since its a animal skull but you might need to do a 'low violence' version without skulls.
Nah Shock I'm quite certain it's all skulls. As far as I can remember WoW had to change all the bone dragons to normal dragons for the chinese version of Wrath of the Lich King
I'd add some kinda subtle rune or pattern on the flat part of the weapon to break up all that space. Keep it simple though, just a geometric shape or two would probably work ok. As others have said, skulls can be a problem, and small details (like the bracer studs) will be lost ingame. The concept is really cool though.
They accept animal skulls on a case by case basis. Giovanny your concept artist should start taking away all the details, it's too much for the game and will read only as noise. In lieu of this your sculpt is starting to look nice, especially the helm. I'd cut back on the superfluous details like the bracer has and start…