Challenge the students to find real-life examples of tessellations. They can bring in something physical, such as a soccer ball or a kaleidoscope, or bring in a picture if they can't bring in the physical object. Have a contest for the most original real-life tessellation find. A variation of this is to send the students home over a weekend with a goal to bring in as many items or pictures of real life tessellations that they can find in their environment.
Give the students tessellation puzzles to put together. These are difficult to complete because of the repeating patterns. Place the students into teams of two and make it a race. The first pair to put their puzzle together wins. Rotate the puzzles around and play several rounds. You can also have each pair of students create their own tessellations, cut them up into a paper puzzle, and challenge their classmates to put them back together.
Show the students tessellation art projects, such as those from Dutch artists M.C. Escher and Victor Vaserely. Team up with the art teacher to help the students create their own tessellation painting. Remind them of the principles of tessellation -- repeating patterns, no gaps and no overlap. You can then have the students display their artwork for the student body in a tessellation art fair. A panel of teachers can judge the paintings and award the top three prizes.
Bring in or create tessellation pictures that use identifiable objects such as faces, animals, and food. Divide the students into teams and show them the pictures one at a time. The teams must collectively figure out what the objects in the pictures are and "buzz" in with a guess, by ringing a bell or raising their hand. If the team that guesses first doesn't get it, the other team has a chance to guess and get a point. The team with the most points after going through all the pictures wins.