The garbage cans don't look right because they're dithered in a flat-shaded world.
A little more of the tops of the cars could be showing. Also, the dithering on them looks out of place for the same reason as the garbage cans.
Might I suggest:
Some blood spatters on the pavement
broken bottles
a little tone variation in the road, some dark spots, like where new concrete was poured over potholes, the like.
Sherman's also very right about the animations being choppy and, well, they don't really have much expression. Like when he swings the bat, he's not really moving like he's trying to bash a zombie but like he just wants to put forth the minimal effort required to knock one down. I'd suggest something like one or two windup frames, then WHAM! he swings that thang at full force, maybe two frames of actual swinging, both at close to full extention, before bringin' it back around, where it waits for a second before he returns it to starting position.
Also, what's with the lifting of the leg?
I think the arm in the punch needs more extention. If a zombie gets close enough for you to hit it at that range seems like the damage'd've already been done.
I still love the hair. Bouncy-bouncy