What species are you planning to house?
For burrowing species, my favorite modification is to use a 20 to 35 gal glass tank and place a plate of glass inside about 2 to 3 inches (depending of the size of stomatopod you want to keep) from one wall. The top of the glass should be about two inches below the water line. Fill the compartment with fine sand and/or some of the commercial "muds" on the market. You now have something that looks like a giant ant farm. Clip on a length of screen that extends above the water line. You can now place your stomatopod (P. ciliata, Lysiosquillina, Acanthosquilla, Squilla, etc) in the compartment. It may take it a couple of weeks to burrow. After it does, you can probably remove the screen and the animal will stay put (except for P. cilata or other species that hunt in the open).
You can grow a few plants in the mud and use the rest of the aquarium for corals, soft corals, etc. If the burrow comes up against the glass, a little black tape or plastic can be used to cover it and still alow you to lift the cover to see how the animal is doing.
My tanks are constructed for observation and research, so I place the sand compartment in the front allowing access to the animal, but I imagine you could be creative and place the compartment on the side or back to form a background.
If you were really lucky, you might be able to come up with a male and female of a monogamous species and establish a pair. Many lysiosquillids including Lysiosquillina, Acanthosquillla, Pullosquilla, and Bigelowina live in monogamous pairs.
Roy