Fortunately, artists are not under the same limitations as scientists and engineers. We can be MUCH more "playful". Imagination and willingness to try new things are essential here.
Some general rules:
2a may not be obvious. Looked at head-on, a perfect pinhole looks round, but as you get further and further away from head-on, the hole looks more and more oval until it disappears. The thicker the material the faster this will occur, but even an infinitely thin material disappears at 90° (edge on). And the smaller the hole, the less light gets through and the lighter will be the image on the film plane.
So in practical terms this means there is a "fall off" in the image away from the center.
This gives us two possibilities:
From this we can add intentionally, a third possibility. Time. One pinhole need not be used at the same time as another, hmm……
(the separated pinholes would produce a stereo pair, hmm, 3D pinhole)
Part of the magic of pinhole is the infinite number of possibilities, but don’t forget the aesthetic side! Good subjects and composition are still the best images. We should not depend on "special effects".
This is an example of the extreme in multihole cameras. 32 ideal pinholes of about 12mm focal length onto 4x5 film.