Where are you seeing your account picture? The only place I've seen Address Book pictures is in received mail. If you're worried your recipients will get it, they won't. That is pulled from Address Book, not something added to the messages.
But, if you really want to get rid of your Address Book picture...
Uncheck the "Export photos in vCards" option of the vCard pane of Address Books preferences.
Export your card.
Delete your card from Address Book.
Import the card you just exported.
Select "Make this my card" from Address Book's Card menu.