Magma Chamber?
http://cdn.pcgamesn.com/sites/default/files/league%20of%20legends%20magma%20chamber%20preview.jpg
Honestly last year at All-Stars I was super excited about magma chamber being introduced but it turns out that Riot decided not to release the map, and I'm sure they have their reasons. Personally i think that bringing this map back could really bring a whole new aspect to the game and i think it would be cool to introduce ranked system through 1v1's or 2v2's on this map would be a cool and new way to play league of legends.