You should take a look at
M.C. Escher's work, and that of surrealists like Magritte or Dalí (although they mixed up objects in an ingenious way rather than just exploit the way our brain processes what we perceive). I had a phase when I tried to copy all of Eschers stuff.
While I like optical illusions, I don't really want the forums to become like BuzzFeed.
And the topic is old.