Why not make some big pentominoes? Or make a tessellation from them? A great book for ideas is Polyominoes by Solomon Golomb.
I introduced them to year 7 and 8 students as part of a unit of work on symmetry. We started by looking at trominoes, then made a family tree for the tetrominoes and finally pentominoes. Interesting questions included 'how many parents does this pentomino have?'