The photo is apparently of the
27-year-old 26-year-old woman shot and killed in Iran on the video reverberating around the world. There's also a photo of a gravesite on BBC Persian. Iran's religious leaders have banned prayers for her. If you want to see the very graphic and disturbing video, it's here flagged by YouTube users to require a sign-in to view.
* Photo update: This image is the one being used by the New York Times, credited to Agha-Soltan's fiance Caspian Makan and Associated Press. Earlier photos may not have been her.