I recently completed a quilt top and quilt back made from clothing of a friend of mine, who died in 2011. This, and a second quilt I'll make, will be for her family. I've never made anything of this size out of clothing before, so that was a little bit challenging. But it all turned out ok. I actually included some seam lines and parts of pockets in the fabric squares.
Here is a little closer photo. I chose this pretty blue batik to border the quilt. I'm going to sew a couple of special buttons onto the quilt top, too.
And here is the back. I used the pretty batik fabric for most of it, then added a strip of solid blue close to one side.
Within that strip is a small emblem from a special t-shirt. I simply put some fusible on the back to stabilize the knit, then treated it like any other fabric.
To figure out the correct fabric measurements for piecing the quilt back, I use precise drafting equipment and procedures in order to get everything to come out to the right size. You can see that in the photo below.