What can live with my ball python in his turarium?

Nothing.

Ball pythons are shy solitary creatures. A 90 gallon tank is way big for a ball python. Bigger is not always better for these snakes.

A plant.

Anything else they'll eat, including other ball pythons. They, like all snakes are cannibalistic. Beyond that they get stressed out very easily when forced to live with other snakes even of the same species.

http://pet-snakes.com/housing-snakes-together

Ball Pythons will eat pretty much anything that moves except for another Python

Absolutely nothing!! Pythons/snakes are solitary animals!! You could possibly house two pythons but snakes are not good room mates for any other animal!!

a mouse lol or another ball python

Possibly another royal of your current one's size.