Because I love Bellatrix and annoy Best. :P

The whole room is filled with all things Bellatrix Lestrang. Slythrin crests anti mudblood posters. Bellatrix posters and some Voldy ones. There's a closet full of Bellatrix's cloth and jewrly and a nice anti-destruction charm on everything. (Why? So Best cand destroy stuff of course!)

(And incase you haven't figured it out yet Best this is just a joke, not trying to be mean or anything. ☺)