It's the newspaper article about the surrender of earth thats tacked up.
On the bottom part of the page is a picture of a man grieving. Here I managed to find the screenshot on google images, and I've circled part of the screenshot:

I recognized that picture from the online edition of the New York Times on September 11, 2001. I was moved by the picture and saved it to my harddrive, and then I saw it in HL2. How much do you want to bet that they didn't ask permission to use the photo?
Here's the photo from September 11, 2001:

As far as I know, no one else has ever made this connection. Someone give me an e-cookie!





