"What would your character crossplay as/what would his costume be for halloween?"
For Halloween, Leon would probably dress as an immortal archer unless he was supposed to be scary. If he was going for something scary, a robot: Arrows bouncing off its steely hide would not be problematic if robots could think.
For crossplay (I googled the term) he would where a big, poofy, dark green and blue dress. It would hold his body in a slightly uncomfortable manner, forcing him to stand more like a human than is natural for a gnoll. Additionally, he would wear gnollish jewelry of the purest gold along with plenty of gemstones. Then, just when everyone thought he was plain ol' cross dressing, he would have a black hand print across his chest. In his hands, he would carry a ladylike parasol made of green silk, with an ash handle. The stretchers would be made of black iron.
What I'm trying to say is that if you're specific enough, people will think you have something to say. Who knows, maybe Leon does.