One of these photos from LGS's final day might be good --
Out of those, I'd probably say the trophy case of all their awards for their games (#3) is one way to get across the message of what these games represented. These were groundbreaking games.
Edit: or you could find one yourself. Here's the first page of those photos: http://www.digital-eel.com/mc/fdays.htm
Edit2: If you want something really iconic from an actual game, the first game in the LGS line that really set the standard and concept of the immersive sim was Ultima Underworld, so some image of that would be good. Maybe an image of the big cloth map that came with the game would be an iconic image for it? -- http://www.uo.com/archive/ftp/maps/uw1/abyss.gif (I mean this was still back in the paradigm total immersion days where they'd put things from the world literally in the box.) Or this shot: http://www.ultimaaiera.com/wp-conten...underworld.png