Aspen, cypress, pine, eco-earth,repti-bark, or paper towels for my snakes?

Aspen, cypress, pine, eco-earth,repti-bark, or paper towels for my snakes? Im getting a corn snake and a ball python in less than a week..i have their tanks set-up with paper towels but i was thinking of puting down something SAFE AND NATURAL...but wat is the safest and best way?should i just stay with paper towel?