Kotaku have posted up some pictures of the new screenshots shown at PAX. They seem to be pre-rendered promo shots using in-game resources:
The other pieces show similar situations where the marines are generally in a whole mess of trouble. I still expect high-res versions online at some point. Visit Kotaku to see the original images. We have some cleaned up versions in the forums. Thanks to Ikarop for the link and for cleaning the images up for us.