Tom,
Since I worked in Photoplate for a few years and did several pieces of art for the Art Department, I'd have to concur with you. Granted there may have been some artists before I was there or after I left who managed to slip something in to make their mark, but I never saw it attempted on purpose from 1977 to 1980. And I think it would have been even more difficult in the following years after 1980. They still had some of the same people behind the the cameras for years after I was there, and I know how difficult it would have been to slip something like this past Brother Robinson or ANY of the others for that matter. (By camera, I mean the cameras that took pictures of original artwork to ultimately create printing plates for the presses.)
When I used to post more often on this site, I wrote up my feelings about it here:
http://www.jehovahs-witness.com/10/56369/827656/post.ashx#827656
I believe it was David Taciak I was talking to (also in Photoplate at the time) who joked with me about a certain artist at 124 who might have been crazy enough to try putting his initials, or some other form of signature, on a piece of art. (David finally got transferred from Photoplate to a permanent position in the Art Dept.) But as I mention in the link above, it was more trouble to keep accidental "subliminals" OUT of the artwork. We'd often see something that came too close to looking like a face in a bush or cloud, or the smear of erasures that didn't "drop out" as well as the artists hoped. We'd often have to shoot something 10 times on the camera to avoid places where we suspected the final print was going to have unrealistic looking water reflections, or shadows that were too strong, or the like. We were pretty good, but sometimes the artist would sometimes see something on the proof that we missed, and sometimes they'd redo it, or we'd touch up the art for them.
In reality, very few of the artists were actually very good at folds in cloth and clothing, or folds in the skin of a hand or wrinkled brow. When an artist is drawing, they will often see a face forming in the cloud and redo it. Even a photograph that might be copied for a picture can have branches making swastikas, and crosses, or clouds that look like a fist "flipping a bird" and the artist is sometimes aware of these problems in a graphic or photograph and UNDOES these things in the art even where the original innocent photograph accidentally created them. (Photos are sometimes too perfect, and don't look natural enough without changes.) But that doesn't mean the artist is going to catch all the subtle things that can show up in his final art AT ALL ANGLES. Some bored person at the Watchtower Study is going to scrutinize a picture from upside-down or sideways and see a face that the artist didn't catch, or a "NINA" in someone's hair.
Also, we were always trying to get used to how the new printing methods were going to treat color and shadow. And then sometimes you guys would just lay the ink on too thick (lol) and it was unpredictable.
I think that a lot of people don't realize that the mind is pre-wired to pick out faces from the surroundings and certain "out of place" objects, shapes and edges - even if these differencxes are extremely subtle. Too many straight lines in nature will jar the mind and make us conjure up a man-made object. Even babies are psychologically wired to pick up on the slightest variations in faces. Everyone sees a man in the moon. Animals with honed hunting instincts have extremely keen senses for picking out "edges" that don't belong: such as fur among leaves, eyes hiding behind bushes. And there have been numerous studies of how the human mind will automatically get tricked to fill in white spaces with imaginary "suggested" edges.
I haven't given much thought to why so many people tend to find "demonic" images. But faces tend to be unavoidable, and especially the ones that are missed in quality control will often be distorted and therefore might naturally look demonic. It's almost a cliche that a frightened, restless child can see a few extra claws and scary faces in the shadows and branches of a tree scratching near his window after the lights go out. Perhaps it's somewhat analagous that those who now see the dark and scary side of the Watchtower will, therefore, pick up on a few more of these problems in Watchtower artwork, even if it's no more purposeful than those random scratchings of branches through the glass, darkly.
Greg