I also used my graph paper and colored pencils. You can also use paper and cut out blocks and lay them out on the table then turn them and move them til you get a look you like. You can sew and iron paper just like fabric so you can experiment with paper to get an idea of what your design would look like in a 3D version.
If you have seen my Boston Blocks you can color a block like that and then cut them out and move them around to see differant ideas.
Or color your squares to look like half square triangles and play with them to see what you can do.