Just want to make a comment about the 2nd picture...
Why do you have an anti-air gun?
Surely if it is a zombie invasion, you wouldn't need to shoot zombies down as zombies don't possess the mental capability to fly an aircraft? Surely you should put something better? Maybe make a bottle neck choke point using terrain with an MG turret? Also, I wouldn't keep 9 (what seem to be) explosive barrels next to an AA gun.