I love this type of teaser image. The guess work is just plain fun. "Is that Wolverine or Beast? Is it Iron Man or Nova? Valkyrie or Scarlet Witch?!"
First of all- THOR AND MS. MARVEL ARE AVENGERS! AWESOME!!
So I see five distinct blacked out characters. I'm going to start my guesses with the figure on Ms Marvel's right.
Looking at the post, including what appears to be the character's hand by his right knee, I think this is Spider-Man. It's a pretty classic "Spidey webslinging" pose, if you can imagine Peter in the space.
The next figure to the right/counter-clockwise looks pretty familiar. I have two guesses from the silhouette. I think the first is more likely- Nova. The gauntlets and shoulder pads, combined with the slimmer figure and smooth lines of the character leads me to this guess. The second guess is an Iron Man of some sort.
However, looking at the character below Thor to the left, I think silhouette matches Iron Man better. It appears to be wearing a helmet, with sharper lines on his arm and hip, which indicates armor to me.
The character directly beneath Thor is pretty obvious- he has wings and appears to be carrying a round object. It's Sam Wilson, Captain America. That's not even a guess. It's a certainty.
Now the figure beneath Thor to the right... that's bugging me. It's a flying caped figure, and appears to have something surrounding its head. That would lead me to believe it's the Vision. But look closely at the character's left shoulder. Is that... armor? Could it be Odinson or Beta Ray Bill then? The shape obscuring the character's head could be a hammer I suppose.
How about an out-of-left-field guess? Could it be Medusa? These silhouette teasers have cropped important details before (Odinson's silhouette on Axis cover previews left off Jarnborn, his axe, and Captain America's silhouette on the same covers left out Sam's wings). What looks like a cape with a high collar could very easily actually be flowing red hair, cut short for the silhouette. And with the increased Inhuman profile in the MU, it makes sense for Medusa to become an Avenger.
Any other guesses?
Right about one, half wrong about another.