Removing account icon from email

My boss is running snow leopard and is unhappy with the user account icon showing up in the top right corner of his emails. How can this be removed?

Example:
http://www.swri.edu/images/mailicon.jpg

They are NOT sent and only show on your Mac.
Change in Address book and/or System Prefs accounts.
Having the ability to add pictures to people in your address book can be fun as they never see it and it only shows up on correspondence from them.
S.