Outlook 2010 comes with a variety of new features, including "People Pane," which allows users to see an overview of the person e-mailing them. Information such as appointments, recent e-mails, and a picture of the sender are available in the pane. Another nifty feature the pane includes is the ability to use Outlook Social Connector to populate contact information from senders you know from social networks such as Facebook. If the sender doesn't have a picture, a default silhouette is displayed instead.
That default picture appears to be, humorously, a picture of Bill Gates with a few of the "finer details" removed. According to ArsTechnica, not only is the picture a silhouette of Gates, its from one of his not so bright moments after being arrested during a traffic stop in the 70's.