I agree that fine-grained things like aren't a great for leos, impactation and all that.
Since they come from rockier places, what about largish gravel like large aquarium gravel? Probably not for babies, but for juvies/adults as a prettier tank look. I'm thinking stuff 1/4" to 3/8" size.
Only issue I can see is that to clean it you'd have to remove all the gravel, wash it, then put it back.
Thoughts?
--Maarken