This may be the greatest links page ever: Larsdatter has the Medieval Beards page.
My (ironic) favorite is Dürer's Self-Portrait in a Fur-Collared Robe. In that image, Dürer depicts himself as a sort of Christ figure -- thereby being one of a small handful of people I'd punch in the face if I had a time machine. Maybe he was so interested in the Protestant Reformation because he thought Martin Luther might start worshipping him.
Just look at him -- the dude clearly thinks he's the shizznit.* What a douchebag.
*You have now read the first occurance of "shizznit" in my writings. Make a note of it.