You can use
ANYTHING as the substrate for your tank, however 99.9999% of anything will probably kill the snake too
What kind of appearance are you after? What kind of enclosure is it? (tank, tub or custom?), what size of snakes are being housed? Do you feed inside their enclosures or in a separate tub?
You really are best being a little more specific about your requirements.
Although, shredded aspen and aspen shavings work well, as well as cypress mulch, for a particle substrate. If you're feeding the snake inside the enclosure (just generally a bad idea, although some people have no problems with it), you're better going with a non-particle substrate, such as reptile carpet (works pretty well, washes in the machine), astroturf (personally I don't like it, it's a b*tch to clean, although some like it), paper towels (good for neonates, or new snakes you need to get a poop sample from to take to the vet).
Answer the questions above, and we'll be able to give you a lil better advice
