I usually use white on white, but for my Christmas Dear Jane (posted with pictures as My Christmas Dear Jane) I used white, no-iron muslin. I wanted it's brightness with nothing to detract from the DJ blocks - nor from the embroidery/quilting on the white. I used it for the backing, too. That meant I had to use white batting, too. When you look at the pictures, notice in the picture of the back that you can see the burgundy batting through the batting and backing!
I buy muslin by the bolt - this was 90" wide white muslin - about the same weight as the rest of the fabric in the quilt. I cut off MORE than I need, serge the edges, and prewash & dry 3 times before cutting what I need. It shrinks a LOT, and I want it to do its shrinking BEFORE I put it in the quilt.