When the server gets more populated perhaps host a few PvP tournaments, winners get prizes etc.
1v1's or 2v2's would be best IMO, but that's up to whoever is hosting the event.
Perhaps if the server gets even MORE populated you could do it by class, have a separate tournament for each class and then pit the winners of each class against each other.
Just some ideas flying around in my head. <3
-Relapse