Last year at one of our men only quilting retreats, one of the attendees worked on his quilt from his shirts. It was just squares - about 4" finished. Random placed and not in 9 patch arrangement. It was really nice looking. My preference would be to not use a defined patchwork pattern which might difuse the fabrics. The shirts were cotton and blends. Since there was a mixture of fibre one needs to piece carefully so any one does not stretch.