I guess maybe the pic was taken much later after it had been killed and is slightly swollen from decomposition beginning to take place. Also with the amount of variation in black rat snakes it is possible that is what it is. But with the head being gone, I think that is the most often used part of identifying them. Plus the position of the dead animal in the pic just makes it look odd and very un-rat snake looking.
I used to catch a LOT of black rat snakes when I lived in Maryland, and thinking about it, they were quite variable even in that comparatively small locale.
But you probably won't ever know for certain.
