From a Religion News Service interview with Thomas Blackshere:
Colorado Springs artist Thomas Blackshear, who typically specializes in African-American themed art, was commissioned to paint the image for the Mother Teresa commemorative stamp.
Q: How do you portray Mother Teresa, the larger-than-life Nobel Peace Prize-winning humanitarian, in a tiny postage stamp?
A: Itâ€™s all about finding the right graphic image. The postal service decided to go with a smiling image that has been seen everywhere. This portrays her as a happy person who loved life.
Q: How was the image chosen and created?
A: The postal service sent me a number of photos, and I created pencil drawings based on three of these photos. One drawing showed her as somewhat somber. Another one was more pensive. After the smiling image was chosen, I created the final 5×7 image by using water colors. I kept building up the layers over three or four days until I got the look I wanted.
Read the full story: http://www.religionnews.com/index.php?/tenminutes/10_minutes_with_thomas_blackshear/