Not really fan art, per se.. but.. I figure some here might get the same kick out of this that I did when I first saw it a year or so ago.
A skin for Bill Rizer from Contra, made to look like Doomguy (using Contra 3 sprites as a base). Made for Super Mario Bros. Crossover. Skin is currently NOT in-game.
And if it did get included, I doubt the portrait would animate as proposed.. they're just put there because those spaces are otherwise empty.
Frozsoul for making the original skin and allowing me to update it
Me for updating it in numerous places
Belial the Hedgehog for the Contra 3 sprite rips
..and, of course, Konami and id Software