Well, there's the leaked Tron-like suit Black Widow was rumored to have! If you look carefully, you can see a Blue streak in the background from Quicksilver's mad dash, Thor's mighty hammer, and Hulk's enormous arm poking through. My bet is that there is a character poster for every Avenger, and that when the posters are lined up side by side, they make one complete image.
However, if my theory is right and they're doing every Avenger, shouldn't we get a first look at the Vision? Yesterday, Marvel released the character posters of Scarlet Witch and Iron Man (see them here), and now two more have arisen today. Marvel's official announcement alongside these posters says:
Headed to San Diego Comic-Con? Don't miss out on what are sure to be some of the hottest items of the convention, these posters featuring concept art from Marvel's "Avengers: Age of Ultron," in theaters May 1, 2015!
Yesterday we showed you Iron Man and Scarlet Witch, and today we've got two new posters for you featuring Captain America and Black Widow. Make sure to stop by the Marvel booth, #2329, to pick up these free posters while supplies last! These two posters are only available today, July 24, while supplies last, and you can check out both of them directly above featuring artwork of Captain America by Ryan Meinerding as well as a poster by Andy Park of Black Widow.