Editor's note: Check out this image from the ISS inside Destiny Module. Look at the upper left hand corner of the image - at high resolution.
Is that a bunch of party balloons? Are they evidence of an on-orbit birthday party? Jeff Williams' birthday is on 18 January. Pavel Vinogradov's is on 31 August. Guess not. However, this ISS status report noted that "Vinogradov and Williams had a day off on Monday, Russian Independence Day" and this image was posted the next day. I'll ask NASA PAO (they deserve a fun question to answer every now and then)
Editor's update: Allard Beutel from NASA PAO just called to tell me that the balloons were actually part of a surprise birthday greeting for Jeff William's wife during a private family session a few weeks ago.