A week ago, we studied artist M.C. Escher. I taught the same lesson to both my little elementary class and to the middle/high school class. It was equally accessible and fascinating for both age levels. We watched a short youtube video about Escher, and then made our own tessellations. Tessellations are flat shapes that cover a plane with no overlapping and no gaps between shapes. It is the way Moroccan and other tiles cover a surface with design, or how a puzzle fits together.
Not everyone wants to alter their shapes into a picture tile. Plain tessellations can be treated as more of a Moroccan tile and colored in a pattern.