The idea of a natural habitat for snakes is a nice one, but it doesn't really work so well. In the wild, if a snake defecates it can move away and let nature do its work on the poop. In a closed habitat, you are the one that must remove the poop; the only problem is, you cannot completely remove all traces of it and it will eventually build up until it is unhealthy. Switching out the substrate every so often would help, but then you'd have to tear apart and re-do the habitat each time.
Another issue with live plants in a snake's enclosure is that eventually the snake will get big enough to crush the plants. And as someone else said, depending on the snake high humidity can cause serious health problems.
I do agree that a snake enclosure with some wood shavings and a water bowl is boring; I use driftwood, rockwork, and natural looking hides, along with fake greenery to make the habitats for my snakes look more natural. It's not the wild... but so far the snakes haven't complained.
What sort of snake do you have?