Single Hole: just that, one hole. Theory, construction suggests, etc. START HERE if a beginner.
Multihole: overlapping images, stereo pairs, or different colors on each hole.
Double Slit: classic fun house mirror effects.
Zone Plates & Pin Sieves: used in X-ray telescopes. Here we use it to give a dreamy effect to images.
Video: gives a bug's eye view of the world.
Enlargers: didn't think it was possible did you? It is. Great place for distortions after the fact.
In pinhole camera tech, you are limited only by your imagination.