PumYo, how about this idea?
After the cup, all teams that played rate all the maps from 0 to 10
The map that receives the best ranking gets a small part of the prize pool.
Honestly, a survey similar to what console and I used for new map pugs would be better than an arbitrary 0-10 so people could see what people like and dislike about each map.
I don't have the exact surveys anymore, but I'm sure console does