I enjoy the challenge of doing NPC portraits. I try to make each portrait unique. Whenever possible I include a background behind the character that hopefully helps the gamemaster get a better sense who that character is and how to play him or her.
The rough sketch of Doug Wiley for Detour doesn’t really demonstrate that so I’m including the final illustration below as an example. In general I prefer to let the final illustrations be only in available in the actual product until the product has had a chance to sell for a while.