So many good ideas here. I know I would love the foam board design wall for all the pluses:
1-lightweight & moveable by most of us without help
2-Inexpensive to start with
3-flannel or batting easily taped, glued or thumb-tacked to the backing.
4-stiff & sturdy for lots of blocks for your quilt layout- no sags.
There is only one thing I plead with any of you to keep in mind: flammabilty.
"Foam insulation is relatively hard to ignite, but when it is ignited, it burns readily and emits a dense smoke containing many toxic gases. The combustion characteristics of foam insulation products vary with the combustion temperatures, chemical formulation, and available air.
Because of these characteristics, foams used for construction require a covering of 1/2" drywall, as a fire barrier in residential applications."
Please don't have your little ones sleep in the room where your design wall is, such as the guest/sewing room. It could be heart-breaking. Thanks and sorry to be the ol' damper here.