Once you pointed it out I could kinda sorta see what you are talking about, but to me it's just random rocks and vegetation . I think our brains are just wired to see and recognize certain patterns like this, like seeing things in the clouds.
I saw something on how we recognize faces, it's a very specific brain function that is different from other types of memories. There is a woman that cannot recognize faces, even her own, although she is otherwise of normal intelligence. That part of her brain just doesn't work. She memorizes clothes people wear, their voices and other things to help her identify people she knows.
While it wouldn't be impossible for the watchtower to put in subliminal messages, there is no proof that subliminal messages work, so it wouldn't gain them anything. If they did put a the image of a man laying down, what would be the purpose, or what do they have to gain from it?