I didn't quilt mine, because 1) I'm really not that awesome and 2) I didn't want to spend that much time. But, I did trim the edges and throw them in the washer/dryer because I still wanted them to have the rag look.
I used denim for the back. I wanted something a little more sturdy and I had a pair of jeans just waiting to be cut up.
It's been fun using them to quiz Abby on her letters--much better that just writing them out on a piece of paper. And, Clara enjoys giving them a nibble now and then.
I has ambitions of doing the lower case letters too...maybe one day.