You could always print your picture on some fabric paper and then attach that on top of the jean block in the middle. Fabric paper is really just fabric attached to a stiff backing so it will run through a printer. The paper comes off after it prints and you now have a picture on a regular piece of fabric. Print the picture so there is a large border around it and then just layer that fabric over the middle jean square and sew them together like they are one piece of fabric, this will make the picture part of your quilt with no need for wonder under or fear of it detaching later.
I think this is a very cool idea, and I hope you post pics when you are done!!
Rachel