All lovers of optical illusions must see the work of Maurits Cornelis Escher (aka MC Escher), Dutch graphic artist whose paintings and engravings are clearly inspired by the limits of our vision and our brain.
He is well known for impossible perspectives like the following:
Or the complicated Relativity engraving:
(You may be interested to notice the CAD work based upon exactly this art work).
But M.C. Escher also worked on repeating patterns and their intrisic complexity for the human mind.
So, I wanted to point you tho the best sources for information about MC Escher and for his best works.