Always loved the original poster but was studying it earlier and spotted something I hadn't before. A face hidden in Nancy's hair.
Bear in mind this is a number of years after Halloween hid a face in their poster, so it could be a thing.
So am I reading too much into it or is it a hidden Easter egg?
I'm not seeing it at all. I'd guess a simple case of what they call "Matrixing" on your part.
There is a much bigger issue with that poster anyway. It's false advertising. Nancy does not sleep topless at any point in the film.
I definitely see it. I'm an artist, myself, and I love putting little hidden images into work. I think artists have always done that.
I just saw it again, and if you look really closely, it actually looks like a bird face, haha.
Here