Underground Desert Biome

Generation and structures:

The underground desert biome would spawn under normal deserts and be mostly made of sandstone. But you must watch your step as the roof could come crashing down which will suffocate the unready player. Quicksand vats would be much like the ones shown in the biome vote, but far more fatal! In addition, fossils would regularly generate, much like the ones in the soul sand valley. Sulfur ore would also generate in the underground caves in large quantities. 

Mobs:

Husks would regularly spawn in underground caves along with a new weathered skeleton. The weathered skeleton would not burn in the day and would have a sandy texture

Plants:

Small pockets of water with cattails and large flowers surrounding them would generate, forming an underground oasis.

Sulfur Uses:

Sulfur could be used to craft gunpowder when combined with charcoal. It could also be used with charcoal and 6 pieces of paper to create dynamite which would be slightly less powerful than TNT.