I play almost exclusively on two servers (same hosting guys) mostly because the lag is not an issue with them like others, but also because the maps are on a set rotation, so there is no broken mapvoting.
One thing I would like to see offered, is a kind of lockout system, where if a map has been previously played, it cannot be selected for voting (similar to how Killing Floor map voting works on some servers) that way, you still get a variety of maps, but also allow some kind of voting in place. One thing though, the map voting part will need to be extended for the extra people voting (killing floor is 6 player per team, unless the server is running a custom mut) so having up to 64 people casting votes in the span of 15-20 seconds can get a bit hectic. Of course, this would be after its working as intended bugfree and then maybe think of adding extras.
For your server, id suggest having a rotation going, if you have a forum or feedback page, leave a server message asking for feedback, those that take the time will benefit from being able to sway how the server plays. Perhaps theme nights where on set nights of a week you have Countdown maps, like Territory Thursday, Firefight Fridays, and then keep an eye on population and see what they like more. At the very least, stick to a set rotation and see how the population changes.