I have used cotton, twill, denim and flannel. I use quilters flannel, not fashion flannel.
I bought someone’s rag quilt project from a thrift shop several years ago. It was with thin flannel with a bandana print and batting. Some of the squares had been sewn together, others were in pieces still. It was terrible fabric to work with. I eventually used it to make dog quilts. It has stood up so far, but has pilled terribly. The dogs do not care.