The Bioshock 2 website is up and it’s pretty good stuff. It reminds me of two of the videos from Tool’s Undertow album.
So if you click to go into the house, and then in the room on the bottom left with the big doll, you’ll notice a black thing that becomes your mouse pointer when you click it. You can’t take it out of the room, and it seemed unrelated to the doll and her pull-string. It really irked me for awhile because I couldn’t figure out what it was for!
Pick it up and draw a sad face or a happy face on the wall in that room. The doll will come to life and the room will change based on the face you draw! I went through all of the other rooms and didn’t notice any large hidden things such as this, but now i’m sure there’s something else.