I found this piece on Deviant Art. It was done by a Russian artist under the screen name Saint Yak. The Nightshade character has under gone several different looks over the years but this one seems to be based on the cameo appearance Nightshade made in the Superman/Batman: Public Enemies movie.
In the previous DC Universe before the relaunch Nightshade a.k.a Eve Eden was an off and on regular non-convict member of the Suicide Squad who had a real thing for Rick Flag. Outside of that her character was a long time love interest of Captain Atom but I never read that title so I don't know much about the history of that relationship. She was last seen in the Suicide Squad / Secret Six Blackest Night crossover. I hope she appears in the new series at some point. Saint Yak did this piece with a combination of pencils and photoshop. This guy is a real pro and it shows in the quality of his work check out the other comic book/ sci-fi related stuff he has on his Deviant Art page: http://saintyak.deviantart.com/