I prefer my backing to coordinate with the front...typically, I choose one color from the fabrics in the front...if I Have something in that color in stash and it fits the theme of quilt, I use that. If not, then I shop for something else. On Queen/King, I like wide fabrics. I'm not one of habit for piecing backs with different fabrics. I did it on one quilt, so far, and would be willing to do again. Just haven't had the need to do it again. Lol....