In addition to the three-dimensional modular origami, I also like to play around with tessellating patterns. The top three photos show how you can start with the same base pattern, in this case simply a square sheet of printer paper folded evenly into a grid of 16 by 16 with additional folds done at 45 degrees through the intersections, and get different results depending on if the creases are converted to a mountain fold, valley fold, or simply ignored altogether.
The bottom two images show how the same pattern can appear very different depending on the paper chosen. Each pair is folded identically – the only thing that changed was the material. On the left in each is simple white printer paper, while on the right are more translucent trace paper and more opaque butcher paper.