1) More diverse maps. The modes don't have to change, but it'd be cool to fight in different locations. Change it up a bit so it's not the same thing again and again.
2) Actually, more modes. Kill counts(First team to 50 kills, 100 kills, whatever.), Capture the Flag, King of the Hill, basic stuff.
3) If possible, make warzone's queue for all servers. Like people in Bastion and queue and be parred up against people in other servers. I'm sure this would increase WZ rates a ton, and would be phenomenally helpful for most.
4) Option to turn off exp gained from WZ's. Some people like being in lowbie pvp's better. Maybe they want to wz with a friend and want to let them catch up.
5) New PvP game, tournaments. Say you get 18 people, in an 18 man bracket, and everyone gets mixed up and have to win a series of 1v1's to win the tourney. Or maybe 18 teams of 4 for ranked team tournaments to see who the best PvP'ers actually are.