This picture was chosen to represent Mercutio. He is the joker of the group and can never take things in a serious manner. Even on his death bed when he is stabbed by Tybalt he is still joking and saying oh it's only a scratch but he is also furious that he was caught in the two houses feud because he didn't belong to either if the families. He is also always teasing everyone about their problems such as Romeos love life but on the other hand he can go a little crazy at times.
I can just see him saying: OUT PLEASE. I have a city to destroy, heroes to humiliate and people to scare, you are just wasting my time. If I ask Nicely can I come out? O forget it I'm stuck! I'll just have to wait.
"Because he's the hero that Gotham deserves, but not the one it needs right now... and so we'll hunt him... because he can take it... because he's not a hero... he's a silent guardian, a watchful protector... a Dark Knight..."