Four new images for this year's, as of yet to be titled Christmas special starring Peter Capldi and Alex Kingston returning as River Song.
Here's the synopsis for the episode:
“It’s Christmas Day in the future and the TARDIS is parked on a
snowy village street, covered in icicles, awaiting its next adventure.
Time traveler River Song meets her husband’s new incarnation, in the
form of Peter Capaldi, for the first time this Christmas."