The first six levels of the Sierpinski triangle in LaTeX.
For some beautiful variations (and more information), see http://www.oftenpaper.net/sierpinski.htm
A drawing in TikZ.
The first picture draws an impossible brick, which induces
an optical illusion similar to that triggered by Escher's
impossible cube.
The second picture draws a Penrose triangle, another similar
optical illusion.
This example helps to show how the isolated areas of a Venn diagram can be filled / coloured.
It was created as part of this answer on TeX StackExchange.
Other options for creating Venn diagrams with multiple areas shaded can be found in the Overleaf gallery via the Venn Diagrams tag.