The Bringer of Darkness, the Oncoming Storm, the Doctor, the Warrior - A Time Lord! http://t.co/Pk1OHkldZy pic.twitter.com/A12ju5CfZ3The women in the picture look like they belong to The Sisterhood of Karn, last seen in the Tom Baker story, The Brain of Morbius. The Sisterhood originate from a planet within the same solar system as Gallifrey, so perhaps they link in with the Time War segment of The Day of the Doctor?
— Doctor Who Official (@bbcdoctorwho) November 13, 2013
The link which is provided with the picture takes us to a page for the Night of the Doctor, which is currently pretty bland; however, the page does tell us that the prequel will be uploaded to iPlayer after broadcast.
The Night of the Doctor will be broadcast on BBC Red Button 1 on a continuous loop between 19:30 and 22:00 on Saturday 16 November.