As far as I know, The Hammerheads only appeared in the first of the Oz books, but they remain one of my favorites among the antagonistic types that live in the darker regions of the Land of Oz; specifically, the southern Gillikin country. You don't want to butt heads with these guys... because they will literally shoot their heads at you if you get in their way.
The Roly Rogues were a different breed of monster, but they do look sort of similar in real life, don't they? Originally appearing in the book Queen Zixi of Ix, Baum moved them to Oz for the movie version of The Patchwork Girl of Oz.
The movie version? Yup. Baum was a lousy businessman and this didn't change when he got rich. A great hunk of his earnings from the Oz books were sunk into The Oz Film Manufacturing Company, which made -- I think -- three films based on the Oz books. Unfortunately, they were primitive even by the standards of the time, and did not catch on with the viewing public. The Oz Film Mfg. Co went bust after a very short time. I put the company logo on the bottom corner basically as a way of crediting the movie still above it.
The deck is now definitely into the back stretch... it's reached the point where I have to be aware of things like balance and structure. The turn into the home stretch is still ahead of me, but I'm getting there. With more than fifty potential base images to chose from, it's time to start getting particular and judgmental.