Seeming that Bioshock 2 is going to be mostly a prequel. One of the greatest things too look forward to is what to expect of the Big Daddy. In the picture you can see a sneak peak of one of the big daddy's experimental suits. One of the new weapons that the Big daddy's will have is an archaic looking wooden cannon. The tank on his back is a lot smaller than what we're use to seeing, and the gloves and pants are more of a leather rather than the traditional Diver suits. And probably the most noticeable change that the "New Daddy" has is the helmet, it only has three sight holes, and they are all forward facing. Whereas the Big Daddy's helmet has multiple sight holes and they give multiple angles of sight.
Update (1/7/2009):I would like to apologize for the incredible rumor on this post. When I saw this picture I jumped on the chance to get something fresh, unfortunately, it was something that had already been released in 2006.
But I feel that just because it was released in 2006 doesn't mean it wont be used in Bioshock 2. Perhaps they realized that the Big daddy was to rough looking, And decided to use that style for an experimental phase of the Big Daddy in the second Bioshock.