An anamorphosis is an image you should view under a very specific angle. If you don't, you'll only see incomprehensible lines.
Can you find the hidden animals in these beautiful drawings?
In each of these mysterious images, a hidden meaning can be found. But which one?
These pictures contain hidden people. Try to find them all!
These artworks all contain a hidden skull somewhere.
Try to find all the hidden objects in these images.
Pareidolia is a difficult word for "to see meaning where there is none". Just think of seeing a teddybear in a cloud, for example.
Subliminal messages are hidden in a way that makes them only noticeable by your subconscious, at least in theory.