The design of Judge Frazer’s bad ass basement is based on the result of a recent joint-study between Popular Mechanic and Spike TV. It reflects every man’s dream basement – a room which contains a vast collection of knives, handguns, big drums of gasoline, buckets of machetes, and crates.
Why the head mount of a moose and a hippopotamus? As we all know, moose is a symbol of the supernatural, the god, the nature*. Thus the head mount of the moose shows the Judge has the will and the ability to kill a god. Which makes him a total bad ass!
Therefore of course, the head mount of the hippopotamus means that Judge is not only deadly on the land; he is also deadly in the water — he is doubly, amphibiously deadly!
Also notice the dis-arrangement of the crates and the gasoline drums around the Judge’s head. It represents the state of his fragile, disturbed, multi-faceted psyche.
*According to the movie Princess Mononoke.