That's looking great, I love the cute style, mainly the regular zombies are a spot-on. The only thing that looks kinda ishy is the 'Gutted Zombie', even though it has to be skinny, it really takes away a lot of the cute style. Also the last potion (the dark purple one in a heart-shaped bottle), looks a bit weird, mainly because of it's shape, but I guess you guys are trying to keep the variation in there, which is good. I'm not sure what the blue potion is, but if it's mana (or stamina or anything similar), I recommend you to make it darker, as people don't associate cyan with mana as much as a more regular shade of blue. But if it's for something totally different, don't mind what I just said.
You could also center the objects in the inventory a bit more, as they are a bit on the bottom of their box now, which looks off.
Further, I really like the level logo's, especially the square one.
All-in-all, good job on the graphics so far, looking forward to the screen-shots.