A waterfall would be a VERY advanced feature for a snake viv. You want to keep it simple until you are an expert.
If this is your first BP, leave him out of the bio-active scenario entirely, and just follow basic care sheet husbandry for several months until you know what you are doing with him.
In the meantime, you can start a viv w/o the snake in it, and not stress on the learning curve and inevitable failures you will have at the start.
A waterfall requires a small pump, and a contained water pool - not the debris water in the drainage layer. Nevertheless, I do NOT recommend any waterfalls for a BP setup, unless you working some crazy huge zoo size of a display viv. ...and even then, too much humidity. Snake's well-being comes first. Last I checked, BP's don't hangout all day soaking in the spray of waterfalls.
I have seen Potos listed as toxic. In my limited experience, it isn't. It is a good plant in both the corn and king vivs. Sanseveria also, should stand up to even a bp, if he doesn't knock it down. I also like English ivy. Get your plants from a herp seller like Josh's frogs, or NEHerpetoculture, so they don't have toxic pesticides.
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