Asa Christiana from Fine Woodworking just did a short blog post on a marquetry technique for recreating an image of a face in marquetry after seeing the marquetry image I made of my daughter years ago. It starts with a good picture of the person you want to duplicate and two different colors of veneer. The photo gets manipulated in Adobe Photoshop to create distinct areas of light and dark (unfortunately I don’t remember exactly what I did but some experimentation will get you there).
Then trace over the borders and make any adjustments necessary to get the borders to flow properly. Stack your two veneers between two layers of cardstock with the drawing on top and simply cut along the lines. You end up with two images, one light/dark and one dark/light. I learned this technique from Patrick Edwards when I took one of his marquetry classes years ago. In the class we used a lightbox to trace around the original photograph but I found that Photoshop gave me a more interesting outcome and more possible variations.