I would tend to think it is either crappy artwork, or some bored Bethelite seeing what he could get away with, before jumping to the conclusion that the WTS is endorsing the black mass.
This.
There's just so much that's demonstrably wrong with this cult that focusing on some perceived "demonic" images in the artwork seems to be not only a waste of time but could possibly steer someone away from learning TTATT when they see that us apostates are insane and obsessed with pointing out every minute perceived imperfection. If you want to complain about the artwork, there's still plenty to complain about - like a little girl falling into a pit at armageddon because she clung to her dog.