This photo was posted on Weird Chicago, and the poster notes that the picture was taken in the Florentine Ballroom in the Congress Hotel in downtown Chicago. The site goes on to say:
No one was walking past at the time, and it showed up on the LCD screen, so I know it wasn’t photoshopped in. It COULD be something like a camera strap, or some other camera whatzit, I suppose. It’s worth noting that the Congress was being renovated – one of the few things ghost hunters DO agree on (every ghost hunter thinks most of the others are quacks) is that renovations tend to [lead] to more sightings.
Here’s a detailed blow-up of the anomoly in the photo: