There is a large variety of colorful advertising posters for international ballet and theater companies available online for decorating. If you have posters from any productions you or your students performed in or produced, consider including them as well.
Another option is to use portraits or photographs of famous composers, playwrights, dancers or thespians either framed or in a collage. Rotate the pictures to coincide with units being covered in class.
Fine-art prints or photographs depicting scenes from the theatre or rehearsal room are also available online for decorating. Choose from artists like Edgar Degas and Jin G. Kam or photographers like Bill Cooper and Harvey Edwards.
For high school students, try using the room to remember students who graduate. For theater, buy inexpensive masks that departing students can sign, decorate and hang on the wall, and for dance, retain an old, signed ballet slipper, tap or jazz shoe.
For a younger class, hang tick cotton or velvet on either side of the room to transform the space into a stage. For a finishing touch, place mirrors on one wall, and paint the opposite wall black.