Sean Lange has added some deft footwork, and a framework to add more animations.
I've also let you drop weapons voluntarily, but there seems to be an intermittent bug with this where the picked up weapon sometimes keeps its unused image, and sometimes isnt responsive.
The (doable) changes requested in previous comments have been incorporated by and large.
I've seriously run out of time this weekend to do more. I'll try to find the time after work this week to add in multiple formation options, kill the weapon bug, and start letting zombies form mobs. The first and last parts should be straight forward, so with any luck there will be a new release out shortly. I'll also use Seans "burnt" art as well in short order, should make burning down a forest even more interesting to watch.