That said, I figure I'll contribute here what I'd probably contribute to the discussion I'll probably miss:
Our zombies don't need raggedy shirts a la typical of the dead walking. There's two reasons for this:
The first, and most simple, given the distance between the actors on stage and the audience in a theater production, small details like a tear in a shirt are harder to communicate than large, exaggerated motions like a cliche zombie walk. Dragging your feet and having your arms reaching out is what would really tell someone you're a zombie.
Secondly, these aren't regular zombies. Regular zombies represent, among other things, the terror of mankind reverting to its animal instincts. The worn down clothes are caused by the symbolic casting off of modern society and its conveniences.
These zombies feed on the financial aid of the student/humans. They represent the aspects of the university that take away our funding; beurocracy in human form, and then stripped of anything that makes them humane. They're The Man without any humanity.
...which is why our zombies totally need to be wearing nice clothing. They still need face paint 'n stuff to look inhuman, but I don't think that the regular "shambling corpse" trope fits in with the deeper themes we're totally going for here.
-Andrew Ben Hartman