These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Yellow Wallpaper
Nightmare Fuel: A case has been made that the "Yellow Wallpaper" that the narrator is ripping off of the walls at the end is her own skin.
In the story itself, the narrator ends up completely insane and creeping in circles around the room. And she talks about this in the most calm way possible, as if there wasn't anything strange about it.
On a meta-level, H.P. Lovecraft considered this an excellent depiction of horror and madness. Think about that.