A great resource for your perusal: The Art of Keeping Snakes by Philippe De Vosjoli
http://www.amazon.com/Keeping-Snakes...keeping+snakes
It goes over bioactive substrates and live planting for terrariums for all sorts of snakes.

I know most people will advise that a BP will just crush most plants you give them, but I have read threads on this forum of live planted tanks that have had success. It is one of those things where it will only benefit you to do lots of research before going through with the idea. Also, the book mentions it may be a good idea to have your tank planted for 3-6 months before introducing the snake. This gives the plants plenty of time to set up a decent root system, as well as giving you time to monitor the conditions and make sure the tank is adequate for the reptile you are keeping.

I have plans for a live planted tank in the future, but have yet to pull the trigger on this endeavour.