I like felt for memory signature quilts (it's better for people to write on). I've used it as a batting for quilted rugs, mug rugs, stained glass wall hangings, table runners (things that need to be flat).

I have used polar fleece in quilted clothing items with great success. It launders well, comes in wide width, and gives a nice structure to the garment. I would think it would work well with a wall hanging. Of course, it would probably require machine, rather than hand, quilting.