Haha Salmeron, your "critique" is so useless it made me laugh, buddy. You could've at least specified which arm, and how he might "fix" it.
I disagree with the artistic direction of using a skull for the head. It's not really a zombie at that point. Give the poor guy some more meat on his bones. I know you want him to look sickly and dead, like your typical zombie, but giving some more girth will increase his visual weight - he's too light.
You ok did on the calves, do the same for the thighs; don't make them straight tubes, give them definition. His left arm has two elbows. Let's give him only one. Why black outlines on only the skull head? Be consistent, or at least use selective-outlining with some sort of plan in mind. He looks to be leaning backwards; off-balance. This sprite needs a lot of lovin'.