Click on above photo if you want an enlarged view of it.One of the most famous photographs of the trading pit, Andreas Gursky's Chicago Board of Trade II has become popular to the point that the print is in very short supply. I've only seen one available on the web and it's for $2500 which is amazing since it cost me approx $50 less than a decade ago. Mine isn't for sale but a friend of mine might be willing to part w/his, email me if interested.
Gursky took the photo from the CBOT visitors gallery in 1999 and also has some other photographs of trading pits which are owned by Deutsche Borse. Some such photos are can be viewed by clicking here. I believe that Chicago Board of Trade II is in the Tate Collection in London.
Another great resource of photos of the pit is Getty Images. To purchase the photo licenses aren't cheap but they have a good inventory of them.