Measure the background of your stage area and purchase three times the length of sheets you would need to cover the backdrop area. Sew the sheets together by their sides. The resulting long sheet should be long enough to completely cover the stage backdrop three times.
Lay the entire backdrop out flat and split the backdrop into three equal parts. Sketch the dividing lines with a pencil. These three sections will be three different backdrops.
Decorate each of the three sections with fabric paint, making three different backdrop scenes. Let dry completely before using.
Cut small holes along the top of the sheet and attach the shower curtain hooks. Do not place the hooks too close together or too far apart, since an even spacing will ensure that the sheet hangs evenly.
Hang the long backdrop on a curtain rod or theater backdrop rod on the stage you will be using. Since the sheet is three times the length of the stage, the first third of the sheet should be enough to cover the background of the stage. As the scenes change, you can easily slide the next third of the backdrop into view, keeping the unused thirds of the backdrop scrunched up and hidden from view.