I like the concept of a 1x1 checkerboard as a mid toned value. In chains I used the checkerboard to fill large spaces to avoid floats and as a third colour when rendering shading in an image. I have enjoyed starting with the checkerboard as a base when trying new ideas, with these faces and also with letters experiments.
Making faces, I used the checkerboard as a mid-tone colour. Adding more light colour stitches creates a highlight and adding more dark stitches creates shadow, used together this appears like a relief pattern, with the appearance of 3D peaks and valleys.Click image to animate
Faces are made up of simple peak and valley shapes. A peak for the nose, a valley for the eye socket, etc. This pattern was meant to look like a little baby doll, with big eyes and a little button nose.