I get level 1-3 most nights. Typically a kind of lava lamp fractal experience. On occasion I get a level 4. Level 4 for me is usually like a high speed slide show of random visual memory frames from throughout the day. Almost like a snapshot low frame rate summary but played back quickly.
I hope you find these links useful and enlightening.
[1] https://en.m.wikipedia.org/wiki/Phosphene
[2] https://en.m.wikipedia.org/wiki/Closed-eye_hallucination
Not as trippy as seeing 'static grain' or static overlay (like static from an old TV) at night in the dark - turns out that is a precursor to a migraine the next day.
I also have known since I was 20 or so that I would eventually get macular degeneration? Is that how thats spelled? (the literal "unbuilding" of the eye...)
I have a floater in my right eye as soon as I turned 47 years old...
but when I close my eyes at night, I can "see" my veins....
I can't say that I see my veins or anything when I close my eyes. Sometimes I'll see big blurry colored blobs in red or in darkness. Occasionally I'll have a twitch or a shiver where I'll see what looks like static very briefly.
I'll occasionally face the sun with my eyes closed and wave my hands in front of my face to give myself a dream machine-like effect, which is relaxing. I would get this sensation when I was a kid and would sit in the car with my eyes closed while my mom would drive to school or church on any given sunny day. The tree branches would break up the sun's radiance as we passed underneath, giving the effect.