lots of wall hangings are made with all kinds of different fabrics, you do not have to stick with cottons; usually wall hangings are made with those fabrics that bleed, or specialty fabrics that you wouldn't want to use in a quilt that would be used, it is common (thought) that wall hangings do not get washed so there are no restrictions. if you plan to wash your wall hanging you will want to pre-wash and make sure all materials are washable together. if you are making a regular wall hanging that probably will not be washed then use what ever. and remember, it is not always the fabric that is doing the shrinking with wash/dry...it is the cotton batting!