I have to admit. I don't. I don't mind the way they look but I've always used just one fabric for my quilt backs.
However. I recently pieced a quilt for myself and when it came time to quilt it I realized that I didn't have a quilt back that would even remotely coordinate or look nice with the quilt top. But... I did have a bunch of solids in my "little" stash that would go perfectly with the quilt top. So Kathleen and I pieced them together in strips and made them into a quilt back. I actually hated them. I thought that the quilt back was going to look horrible with the darling quilt top. But I was in a hurry and needed to get this quilt done.
When I finished machine quilting this one and took it of the long arm machine the first thing I did was turn it over, and much to my surprise I LOVE how this quilt back turned out!