I like the idea of using the plain parts for backing. Tshirting is so soft and cuddly.
I also save the backs and use them to make kids shorts for pjs bottoms. Keep 'em here for the grandkids. You can also use the backs and sleeves and make more tshirts for the little ones. Free fabric.
I've also toyed with the idea to make tied comforters for donation to homeless shelters.