Almost There!

i'd make some adjustments to the various line widths of your elements - especially the girl. the lines themselves need to have a little more personality through tapering, different widths, etc.

i see you've started to do this, but i'd think about taking it a step further and really committing to your linework to give it a little more life and character.

it looks like a good concept, but you need to adjust/think more about the final art. the background gradient does not help much

I like it. Add more details to the face

more zombie stuff? If that kind of stuff really sells that your design is fine, even pretty, if you can say that considering the subject matter I find so unpleasing.