As for loaded and unloaded cars, I wonder if you could load the car with some animals on one side, but put in some sort of baffle or curtain on the other (safely back from the slats). Then the cars would appear loaded from one side, and empty from the other. At the start of of an operating session, they could be turned for the appropriate loads/empties direction.
Except I think the most striking feature of an empty stock car is being able to see through to the other side.
