UPDATE: A bumper crop of scans from the actual issue have made their way online thanks to ComingSoon, and you check out all four right below before moving on to the original post.
As the watermarks indicate, all three images debuted over at EW, where you can see all three, as well as the individual promotional images that were combined to form the magazine's cover. Also, keep in mind that the issue will be available to actually, physically purchase as of tomorrow, September 30th, and it will no doubt contain more Marvel-approved pictures.
It appears that we'll be seeing some big action taking place on a rather roughed-up bridge.
As usual, Mark Ruffalo's Bruce Banner is the odd man out here, no doubt owing to the fact that his superhero-mode is a digitally-created green behemoth. Hopefully we'll get a good look at the Incredible Hulk fairly soon, however. Also not present or accounted for in these stills are Samuel L. Jackson, Cobie Smulders, Clark Gregg, Stellan Skarsgard, or Tom Hiddleston, who reprises his Thor role as Loki, the God of Mischief who calls down whatever menace the titular team battles in the film.
The Avengers assemble theatrically on May 4, 2012.