1. Some of the effects like the dancing stars around the moon are in the category of
Dream State Synthesis which happens only with higher dosing. The most astonishing ones to me are when you are very stoned, and you turn around deliberately and it seems like you can still see behind you as well as what you are now facing, even to the point of seeing 360 degrees instead of just a narrow cone in front.
2. While some geometric visions require the full
dream synthesis ability, at medium dosing, wall paper effects often called
polyopia, which has repetition often at a regular spacing - like geometry, and
pareidolia which may be regularly spaced interval visions, or in which visual cues at any spacing all become eyes, faces, animals or hands.
3. At Lighter dosages visual effects like stars or feathery mandalas around lights will occur and these are partly due to pupil dilation while otherwise they seem to be produced by visual processes similar to diffraction and interference. The more stoned the more detailed the mandalas or feathers of light and rainbow will be.
for #1 to work - to seem to see behind you after you have turned - persistence of visual experience is at hand, essentially a large block of experience fades more slowly even as new experience is happening, and they superimpose and mesh into a new reality that is more incredible than 3-d.
for #2 to work - the same mechanism is at play - persistence with regular interval - elements in a progression persist (like tracers) and rows of elements persist and propagate following a body gesture (like scanning the ceiling looking at hieroglyphics) or idea like geometric progression or alex grey paintings or chackra visualizations.
for #3 to work - diffraction grating type mandala's around points of light, we can easily imagine that interference of energy fields in the visual cortex are producing the effects, this also is supported by longer duration pulse trains from each individual rod or cone.
over all, the effect in consciousness is that sensory input (and ideas) are still mixing in the brain as usual, but each signal is lasting a bit longer (duration persisting by dose effects).
the kinds of chemical changes that we note from psychedelics are synaptic serotonin receptor facilitation which could easily support extended neurotransmitter response, or longer signal pulse trains for each affected group of neurons.
I think that this ties back nicely to the three descriptions I have listed above.