Get some gorgeous dark red velvet curtains to hang around your window or even along an entire wall. Buy theatre posters (vintage ones like Fiddler on the Roof, Phantom of the Opera, etc. look the best) and hang them along the remaining walls. It would be cute to make a collage of theatre productions you're in, both backstage and on. If you can use a lot of dark reds and blacks like theatres are colored, spotlights and chandeliers would be awesome for lighting -- I used to have a spotlight that had colored screens you could pop in and out for a neat effect. Make sure you have a fresh bouquet of flowers featured for the star of the show!
