As seen on Capcom-Unity:
The artwork's unveiling was followed by this ever-so mysterious tease...
"Congrats Unity members! You've survived the social networking challenges and have unlocked this brand new Mega Man 10 art. What's so special about this? Well...here's a hint. There's a third. A third what? Tune in tomorrow to find out!!"
What could it be? My money's on the unveiling of the third playable character, who I believe belongs to that arm towards the bottom. It's gotta be connected to somebody, right?
UPDATE: Well what do you know, the two pictures combine...
Perhaps tomorrow will bring about a "third" picture that acts as a bookend?