One of the papers is the image seen above, which is a drawing of the same Big Daddy doll seen in the BioShock 2 trailer. One of the letters describes the doll a bit: "The head resembles a helmet, the feet could be heavy boots." The letter speculates that the doll "resembles particulars" of an "attacker" that carried out a recent kidnapping.
We're presenting the trailer again after the break, in the hope that one of you BioShockologists will see some new connections between the material on the site and the trailer. Let us know in the comments!