Quilter's flannel is usually made of cotton, so if you want a cotton quilt you could still use flannel. I've used corduroy in rag quilts (mixed with flannel) and have seen many made with homespun, which frays well. But I tend to agree with thimblebug that a rag quilt might not be comfortable to stand on, and it might also slide around easily, which could cause someone to fall. I have a couple of quilts that I made from heavier fabric samples (the kind you might use for upholstery) and I use them as throw rugs, but not in high traffic areas.