When I taught 7th grade for six years visual patterns were used to start the school year because they did so many great things for students. They were engaging to the students, visually stimulating, allowed all students easy entry to the math involved, worked great for student projects, and addressed many math standards. Here’s a site with a lot of patterns you can use in your classroom, along with commentary for teacher use.
As of the date of this post (Sept 2014) there are 145 patterns, along with the Equation Key. Fawn Nguyen is the host of the site, and teachers/others are encouraged to submit patterns for others to use. She has another site, Finding Ways, that in her words: “is where I tell stories that are mainly about teaching and learning mathematics in the classroom.”
Take a look and be prepared to find some nice patterns to use when teaching linear functions.