So THE CABIN IN THE WOODS featured a cast of nobodies. And the poster? It was brilliant!
Take a moment to really appreciate it; admire the detail. It tells you everything you need to know - everything you want to know - to draw you in. You don't need anyone or anything to explain or reference for you. No one needs to hold your hand. You look at that image and you know exactly what's going on even though you may not know a thing about the movie.
When critics got onboard with the movie and it was time to release the positive blurb-age, this was also done elegantly in a way that respected the original poster's reason for existence.
But though these look great the fact is, other ideas were in the pipeline. Someone wanted to step backwards. Someone didn't realize that they were the person Whedon and Goddard were mocking.