The general rule is that exposed skin should be covered by something. It doesn't have to be furs or cloth... an off-colored base coat of makeup is sufficient, but basically, you should not look like an animal-headed human (ala much mythology, Egyptian being the most obvious). When I get a chance, I'll scan in the pics of me as Cat during the first corn-field event... basically, from the waist on up, I looked like Tigger, to some extent.
Back in the day, there were a bunch of us that wrote up wild elves so that we could run around in loin clothes and barely anything more during the hot Texas summers.