I think a lot of people would agree that the same 5 maps are played 95% percent of the time, with the occasional "bad" map being picked to only be instantly RTVed. I would think adding a small incentive to voting for and playing underplayed maps could spice up the usual rotation a bit. Adding a small boost to point gain, both passive and active, would be a good choice. Something like 15% for somewhat underplayed maps, up to 30% for never played maps. These values are just an idea, they could certainly be higher or lower. The point gain would be restricted to non-spectating players so that point farming would stay as it is. I would also think the map voting interface would need to be changed to accommodate this addition so that people are able to see the % increase associated with the map. The incentive doesn't need to be there every map rotation either, maybe every third map vote or after a certain amount of time since the previous one. That way people aren't feeling forced to pick a terrible map all of the time to get the benefits and the usual favorites will get plenty of play time. Could be a terrible idea though, so let me know what you guys think.
I think an easier solution to this might be to extend the time maps are locked for. I don’t like the idea of people voting for maps for points at the expense of general gameplay experience. But who knows, this is an interesting idea.