Pretty nice. Although in my opinion, it has too much wrinkles but i suppose it depends on how you imagine zombies as so it will not affect my rating. You could work a litle on the blood, I think it needs to be a litle darker. Overall pretty good icon 4/6.
Ideas:
Add a definition of a pupil, i know many zombies dont have it but i think it looks a litle strange ( i mean not in a zombie-strange way lol ) so you could just add a litle white stroke. Rip some of his face apart, showing liek brain or something. You could make the background a diffrent color, imo red looks strange.
Ideas are just my ideas, just want to say what i think would look cool. Doesn't mean am always right.
-Somnium