There are no rules for quilting. You can do what you want. If you want to use clothes, go right ahead. I redid a quilt for someone a while back that the whole top was polyester clothes. It has a sheet for the back and was hand tied. The sheet was falling apart so she sent a new sheet for the back and I quilted it for her. The polyester showed no wear at all and she used that quilt for over 20 years. It was her favorite quilt and she always used it.