M.C. Escher instructional worksheet for advanced tessellation design and 2 pages of examples. I found that the basic tessellation was... well, too simple! I wanted to challenge my older students and they succeeded. The trickiest part is making your template shape and I couldn't find a decent instruction sheet so I made my own. 
 
I use this along with my study on Optical Illusions worksheets and my Art & Geometry/Math: M.C. Escher Drawing Impossible Shapes & Tessellations