If I remember correctly, the raised bits of your embroidery will be stumpwork as Mama says, there is usually a backing material which slit open behind the needlework and then some sort of padding is pushed in to raise the stiching which is on the front of the material. Modern metallic threads tend not to tarnish so you must have some really old threads. It sound a very nice piece of work, you might think about using it as a "hanging" if you don't think it would work along the back of a sofa. You'd need to find someone who could put a "channel" through which a small pole could be pushed in order to hang it on the wall.