I made a denim quilt from my sons jeans that no longer fit them. They are children sizes 8 and 10. I love the look that the worn knees added to the quilt. I'm going to make another one that I have with larger size 12 jeans.
To give credit where credit is due. I followed this tutorial for making the denim quilt: http://www.pieceandquilt.com/2010/01/simply-denim-quilt-tutorial.html
Below is a photo of the back. I used flannel.