Remember, there are no quilt police, with that said.... Sure you can piece your back, I have done it but I do not like to do it. I purchase 108-110 inch material at my LQS or order it from Keepsake Quilting and use that. I have numerous Longarmers tell me they prefer that, but of course do the pieced backs too. I like the looks of some pieced backs with extra fabric and blocks in it but I'm no good at math and it takes that to figure out where to place that stuff.