I make a lot of wall hangings. To get it to hang nicely it needs weight. If you have anything heavier that quilting cotton to use as a backing, that's a cheap idea. Batt it as usual. I use cotton canvas as a backing and quilt through the canvas. Then if you like you can cover the canvas with a thin cotton. Hope I haven't made it sound too confusing. The heavier it is the better the sides lay and the corners flat.
MaryKatherine