I'll be the voice of dissent here. Sorry all. I would use whatever fabric compliments your quilt top. If it's all cotton I would use cotton or bamboo batting, both soft and natural, less wear on the cotton fibers of the top (assuming you used 100% cotton on the top). I know a lot of people like and believe that piecing the backing is the thing to do but as a LA'r it makes it all the more difficult to get good even stitching both on the front as well as on the back. Those machines glide so smoothly and every little seam is like hitting rutted out railroad tracks. It makes it more difficult when you can't see where the seams are coming on the back as you work on the front also. If you're going to hand quilt, each seam will mean double the amount of fabric you have to shove your needle through and makes for more difficult even stitches though in hand quilting it's easier to keep an eye on the back to see where you're going to run into them. Just saying. I hope it helps.