Now don't laugh.. too hard anyway... Reading the Newspaper just might help you with your portrait quilting. I kid you not. If this helps you, we better hope the paper rag papers don't disappear or at least the same image will be part of online papers. Some popular papers use some internal software to translate pictorial images of their reporters into a dot image matrix. Check out the above two images clipped recently from a well known east coast financial paper. Click on images for enlarged view.
The two above almost look like stitching. Cool!
The images below are from another west coast paper and seem less clear but still maybe helpful. These printed images began smaller than those above so that may have something to do with results shown here.