Me and my friend went by on this one. We're pretty sure we have it figured out, and in order to maximize the likelihood for gamers to get into the game/speed up tournament outcomes and waves so we can have a good flow and chance of winning for everyone, we decided on Nacht Der Untoten (the first map in World At War).
The way it will work is like this;
if we have more than 12 teams (composed of 1 - 4 players):
We will use 1-3 TV's depending on the amount of sign ups we recieve.
Average run time/wave survival after a few runs with my friend (we're decent at zombie survival) is about 12 to 20 waves.
A good team that can prove they can survive the zombie apocalypse will probably get to wave 30+, but must be diligently prepared and ready... just like a real zombie survival!
We are still deciding if it's a tournament style competition or score based competition on whether or not your best of 2 runs is the best option. I think a tournament would be far more interesting, what are your opinions?
Prizes affirmed will be $20 and my own personal blatant advertisement of my webcomic!

2nd place runners may get Emergency Eye Wash comic t-shirts, 3rd place runners might get something as well. So spread this to anyone you think might be interested!