Very attractive set up. You might want to consider more vertical room. If the mantis sheds over your "Furnishings" it is no different than having a container that is too short; you get a mismolt. As a nymph, this is probably not an issue, but as growth occurs, thin out the forest so you don't restrict where the mantis can hang from to molt.
Barks and dirts don't hold humidity very well, and are messy to keep the container clean, but if you are willing to spray often, will work.
Doing the setup is 1/2 the fun!!
CHEERS!!!
Nick Barta
Mantisplace.com