Cotton batting would work well. I use flannel. I pieced a couple widths together, sewed small plastic rings to the top and hung it on nails pounded into the wall. Yep, I'm just that fancy! You will love having a design wall. I have become a much better quilter since using one because it gives me the opportunity to actually see the whole, rearrange pieces, check values, etc., without having to worry if someone is going to come through the room and disturb everything.