If you want to see seat maps, you can look on www.itn.net which will show them for several airlines.

Once you book your international flight, the DL seat maps will be available when you look in your itineraries on delta.com. One cautionary note: The Skyteam or codeshare flight's seatmaps are NOT available. If you try to change your DL flight, the partner airline seat assignment will be erased! (ask me how I know this!).