I was introduced to this concept years ago when I read Rachel Ashwell's books. Ashwell, founder of "Shabby Chic" style, advocated using the back side of cotton fabrics (chintzes, for example) for projects such as pillows to create a soft, worn, vintage look. Here is an example of this concept in action. This photo shows the front of a bold Ralph Lauren fabric (this is a sheet)--the second photo is the back side of the same fabric:
Not all fabrics are limber enough to accomplish these acrobatic feats, but this is a good tip to keep in mind when you are refreshing a room on a budget and trying to work with what you already have. Remember also to think like a Martian. Whether you're looking at curtains, sheets, or a tablecloth, it's all just fabric in the end--fabric that can potentially be transformed into something else!