My avatar is actually the back of a comfort quilt I made. I had planned to do the back all in one fabric, but didn't buy the backing fabric at the same time I bought the fabric to piece the top. When I completed the top, I didn't want to stop working on the quilt until I could shop for the backing fabric and started piecing together leftovers from the top and added some fabrics from my stash. I ended up liking the pieced back as much as the top.
You could be very creative with what you do and put a strip at the top and bottom, or do the frame of the whole back like someone suggested. Piecing the back sure adds a lot of interest.