Although taking screenshots of the DOOM 3 multiplayer at QuakeCon is a big no no (so I'm told), Activision/id have released two shots for us to munch on:
Click on them for the higher-resolution shots. They were originally released in a massive 4000x3000 resolution (which we're not going to be hosting for bandwidth reasons ). The huge shots can be found over at HomeLan Fed and ToTheGame.