I didn't mean to imply that there wasn't an ulterior motive to the image, Jim, just that it probably didn't appear from whole cloth in Kubrick's mind.
And, honestly, it wouldn't surprise me if the various comic creators and the 1910s artist who did the poster also had innuendo on the mind. Keep in mind the big WWI poster everybody's seen, with the gorilla German carrying off a scantily-clad young woman, after all...