What should I do with my brother's old room?

My mom said I can have my brother’s old room, if he doesn’t move back in. And even if he does, he can kiss my ass!

What should I do with it?

Here’s the layout of the room. There’s a spiral staircase at the bottom, & the ceiling slopes downward from the middle. The room is about 30’ horizontally. And there’s no door. There’s also a window leading to a balcony in the alcove to the left.