I did one for a neighbor and she didn't want anything on the photo itself or at least on the face of the person which I could understand perfectly. So I made patterns that would frame around the face but still leave it bare. She seemed to like what I did. I had the same question for how to treat a quilt with embroidery and someone suggested to use the same color thread as the background of the block in question. I stitched right over the embroidery which was actually a colored redwork and it looked just fine. Good luck on yours and I'll be keeping an eye on the suggestions submitted in case I ever have to do another one.