I acknowledge certain shapes or combinations can suggest a face or random item to a viewer. Anyone viewing clouds will often remark on how the shape 'looks like 'the Queen', 'a Bat signal', 'a giraffe', whatever.
Some of the things suggested to appear as ' ...' within WT literature, I agree to being a stretch, very vague and difficult to be consistently recognized as being the item claimed. We all are unique in both experience and in how we view things. One person in ten may see something which the 9 others cannot, even when the person seeing it tries to point it out.
There are however, too many images which are too obvious to ignore. It's one thing to see portions of something such as a human eye or other facial part, but it's another matter when it's a complete face or other object which is plainly recognized, even if after being pointed out to a casual observer.
I recall my father (an elder) had possession of a published book on WT hidden or subliminal imagery, given to him by another elder. That was over 40 years ago. I remember that book was filled with examples, many of which were plainly evident. I also recall, there was a certain 'appearance', 'style' or 'emotion' to each, which seems to be consistent even to the more recent ones I've seen.
I won't speculate on reason(s) why images would inserted, but this has been going on for too long and with a high enough frequency, for it to be a matter of coincidence.
While some may foresee someone from the illustration department leaving bethel and 'spilling the beans', who is to say the entire department would be involved. Perhaps there are a few 'special' illustrators who are trusted to review and modify the work of others. This now could easily be done anywhere in the world, compared to the past.
With regard to images in other publications, what other publications are these types of hidden images consistently observed?