This is very clever, you pull it off very well. However, I might suggest a cape. A short one. Also, perhaps a change of back ground. Something a little more gritty, rather than lit up. Perhaps the scene of an investigation, or a villains base in preparation for an attack. A warehouse, or dock type of a thing. If that is possible, i'm not sure if you're using a "green screen" or not for back ground effects. Also might consider a ledge to be seen looking down from with a gothic theme to the building. Something traditional in that way.
The cosplay itself is fantastic, even without the cape (Seeing as Robin does run around YJ without his cape at one time). The attention to detail immaculate.
The pose is a little awkward though. It almost looks as though the cosplay was caught between changing posing. It needs more strength. Maybe bend the knees more and square yourself towards the camera. The lack of expression on Robin's face also makes it look like he was caught unaware.
I know it's very hard to give expression with a mask covering your eyebrows. A Few tricks I do is: Clench my jaw, scowl, or give a little smirk. Doing nothing on top of wearing a mask just makes a cosplayer look dead.
But overall: I LOVE the costume and the wig. The Cosplay is very good! C:
The photo itself is definitely not a bad one, I very much enjoy it. I just wish you had found a place with no people in the background--I know coming by places without people can be hard, especially at a convention or in a city--so I'd suggest playing with your angles as best you can to try and keep the people as much out of the background as they can be.
Making sure Robin isn't dead center in the shot would make the photo more interesting as well.