Ok, kind of repeating myself. But you should check out some of the stuff they did on the Zombie Infection servers.
They added "bases" in places like devil's castle, polana and klen (on the top of the mountain, near NEAS) where it looks like people tried to make a stand or medical facilities were set up. They also just added a huge mess of broken cars between elektro and cherno, complete with loot spawns and even a train. I don't know if there's any way to get something like that for your own server, but it may be something to look into.
I feel that it really improves the atmosphere, while not giving you too much, and helps the "story" in that it gets you thinking "Now, I wonder what they tried doing here before they failed".
Also, I do wish the auto fuel worked like in regular arma, though it shouldn't be any faster than using the jerry cans. I was thinking the other day that it would be cool to add something like a manual fuel pump. It would take up like 8 spaces and wouldn't refuel any faster, but it would keep fueling until you cancelled the action.
As it is, I can land right by a tank and just continually refuel for 20 minutes and get a full chopper by myself.