I really enjoy this technique. Over the last few years I've made several of these doodle-y quilts. I have a sketchbook of swirly doodles that I drew with quilting lines in mind, but ended up using the designs for fabric shapes instead. It's so much fun to cut out the shapes and then separate them onto two backgrounds to get the positive and negative effects. This photo is of two little quilts, about 9" x 12" each, sitting side-by-side on the interfacing and backing so that I can quilt them both at the same time.
Did I mention that I love my APQS George? It's doodle-tastic!