Vertical Plains

The Vertical Plains (or some other name) would be a sub-biome in mountains or mesas that would be nearly vertical. It would have grass, stones, and some trees growing off the side. Almost no mobs could live here, but rabbits and birds would. There could also be a new boulder block that would fall down the cliff if there was too much noise pollution and damage any mobs that get in its way. This could also be used for traps.