My first project

Now that I've finally bothered to look for an official working wowmodelviewer, I'm working on my first project. I'm trying to recreate the good ending to Fallout 3 with WoW backgrounds and characters. Just a concern. I can't figure out how to put guns on characters' backs. I'm willing to replace the guns with swords if I can't sheathe the gun onto their backs, but if I can I'd like to know.