I made my denim quilt before I even knew what rag quilts were. I pieced the top from denim, used batting, and chose a bright berry fabric for the backing. My family uses it as a picnic quilt, it is a favorite. The quilt is very sturdy, and grass falls right off easily when packing up. Be sure to use a backing that won't show dirt! The only downer is that the bulk required that it be a tied quilt, which I am not fond of. Sometimes when the kids are sick in the winter they want to cuddle with the picnic blanket!!!
Hope that helps!