The best way to get a moss background is to use a moss mix. Folius has some of the best around. You make a slurry with it and paint it on. A little moisture, a touch of humidity and a lot of patience and you'll have a wonderful moss wall. You can get it at www.folius.net or see Paul at vivariums in the mist. Paul is based on Long Island, so shipping would be pretty quick for you, I would imagine.
Education is the most powerful weapon we can use to change the world ~ Nelson Mandela