I've updated the Zombie Creator so you can change the brightness, contrast, hue and saturation.
More clips are on the way this weekend plus the ability to use your own PNGs. :)
Another idea put forward in the comments was to have film grain, which I think is a great idea. Is there anything else that you want?
check out the zombie creator here:http://www.newgrounds.com/port al/view/552036
and check out the gallery here: http://zombiecreator.com/gallery