1. You can rate the maps with a button on the game summery page with the button on the bottom left.
There you can also leave a comment
2. You can search a map by name when you are on the "map" tab while creating a game.
3. Maybe a bad map-filter is set. If you change the filter to "All Maps" you should see more.
Edited 1/11/2016 13:51:12