FBF,
Show me what piece of art you are talking about and I'll give you my opinion.
There are a lot of reasons to use illustrations (draw style) instead of photos. In the case of the watchtower it is hard to create a large setting of ancient Egypt or Jerusalem to put people into, dressed in costumes, so they can take a photo. It is a lot more cost effective to use the slave labor they have in their illustrators. Also shooting pictures of seven headed beasts, angels, demons, people falling into big cracks in the earth, and cities being destroyed by fire and brimstone are hard to come by and scares the hell out of the photographers trying to shoot them.
I think that is the question you were asking. If not then I'm not sure what you are asking.
Mike,
Illustrators do slip their name or initials into illustrations. I do it all the time. You just have to be careful you're doing it for a client that wouldn't get pissed off and that it isn't real noticeable and detract from the illustration.
Slipping your initials into a woman hair is very likely if not to obvious. Playboy slips their little bunny logo into each and every cover. They have even retouched it into a models hair before.
If you have any questions about airbrush just let me know, I'll be happy to answer them for you.
Dave