UPDATE: The following video shows a surprise cameo in the film. Only watch it if you want to know who it is, of course.
A whole bunch of behind-the-scenes photos and video from the Strasbourg set of Sherlock Holmes 2 are now online, courtesy of French website CineWebradio.
Though no specific plot details are currently available, the sequel is said to include Professor Moriarty as the film's villain (to be played by Jared Harris) and supporting roles for Sherlock's brother, Mycroft (Stephen Fry) as well as an unspecified female lead to be played by Noomi Rapace.
As you can see below, the Strasbourg streets are being dressed and filled with extras to match period France. Click on any of the images for more stills and video at the French site.