I remember playing peter jacksons king kong (the game) on my old ps2, and thought that one of the really cool features was the addition of an end game museum. You could walk in, and see 3D stills of all enemies youv'e en[censored]ered throughout the course of the game. Additionally, there were many background images of the concept art on display. A more popular example of this would be in Modern Warare 2, as they had done the exact same thng (with some easter eggs involved).
I was thinking that it would be a very cool addition to the main-game, so that once you finished [the game] all enemies, vehicles, guns, people met and more miscellaneous things would be put in there. It would be perfect for a game like this, seeing as how certain enemies or friendly AI would only appear once.