Shodar have created a fun Interactive Tessellation Tool which generates lovely small images in a variety of colours.
It is based on three, four and six sided shapes being tessellated. This would make a great group exploration task and generate a brightly coloured maths display for the start of the new term. Just dragging the edges of the chosen shape (rectangle, triangle or hexagon) gives a great tessellation with many different colour opportunities.
This tool is very simple and is recommended as an introduction to tessellations. It would also make fun homework activity for the summer, especially if tessellations were going to be covered in the following term.
It does not incorporate two shapes or rounded shapes.
Interactive Tessellation Tool
There are masses of worksheets and ideas about using this tool under the Instructor Button.