My church quilting groups uses whatever comes in. Sometimes the quilts turn out a bit strange and sometimes they are just cute. All of them will be used for something. Fabrics I have come across, included lots and lots of sheets, usually used for backing and we have one member who will dye any white ones that come in, upholstery fabric, knits fabric, old linen tablecloths, denim, polyblends, and left-over quilt fabric of a wide variety of ages and quality. And the material we use to tie them include sport weight wool yarn (the best!) sock yarn, embroidery thread, regular yarn (hard to pull through the sheets). It is all good. Occasionally, someone will donate some hand stitched quilt blocks which are a bit harder to deal with as sometimes the stitching isn't secure and the blocks may not be the same size.