I know it's late. Christmas decorations in Lucerna passage. And you've probably seen it here already :)
For those in Prague: There is a series of interesting films and documentaries in Prague Municipal Library at the end of January. I'm going to see Annie Leibovitz movie (once again) on January 22, and try to catch a few more. Wish they could start at least an hour later. All info is at their website. And if you prefer Aero Cinema, they have Annie the same day only an hour earlier.