I experienced "visual snow" as one of many neurological problems associated with a non-psychedelic drug reaction. As my other symptoms began to resolve, the visual snow did too. I have had migraines with and without aura. The aura kind of looks like a more fluid version of visual snow I experienced. The snow usually only kind of vibrated, but at the worst could be almost like a strobing visual field.
Since the visual snow resolved, I have noticed that some circumstances can result in weirdness with my vision that mimics it...these are things that are, for the most part easily changeable.
I don't know if what you are experiencing is truly visual snow because there is a good possibility that you may simply be noticing some things in your environment that you weren't aware of prior to your intense LSD trip. These things can mimic the visual snow effect.
Now, if you haven't already, you should see a doctor just to make sure that everything is okay with you health-wise.
If you haven't had your eyes/vision checked in the last year, please do so immediately! I started to experience the visual snow effect again about a year ago and panicked thinking my neurological problems were returning. The symptoms resolved immediately upon receiving a new pair of glasses. My right eye's vision had worsened from 20/30, to 20/75 while my left eye was still 20/35. The visual snow effect was from looking through one unfocused and one focused eye.
White wall and computer screens...if you live in the US your power is likely 60 hertz. If you have not changed the settings for your computer monitor, the default setting is most likely 60 hertz. Now, most people do not notice and therefore aren't affected by this...but there is an annoying fast vibrating flicker to TVs/monitors (default 60 hertz refresh rate), and fluorescent lights.
Fluorescent lights alone, can definitely cause a noticeable visual snow effect when you look at white walls. When I watch TV or especially sit at a computer for hours on end, I experience the visual snow effect AFTER I get up and wander away. This happens only when the screen has less than an 85 hertz refresh rate (you can change the refresh rate for most monitors, and some TVs). It can persist for minutes to hours afterward. It seems like the flicker from by the screen settings causes some type of benign flickering visual artifact...I notice it is more obvious if I am in a dark room trying to sleep just after getting off of the computer after working for hours on end.
Have you ever heard of Synesthesia? It is a (really cool IMO) condition where some of your senses kind of overlap. I see some sounds. I always have. I thought everybody did. Didn't realize it isn't normal to have pale pale pale pastel almost imperceivable patterns and sometimes fractals play out in my visual field. If something like a fan is making 'white' noise in a room, I can see the basic shape and location of everything in the room with my eyes closed. If you have this, and you don't know what you are really perceiving, the image can appear to be "visual snow." Frankly, it usually looks like you are seeing your room through a bunch of static when in fact, you are 'seeing' the shape of your surroundings through your ears.
Finally, when was the last time you took a multivitamin, or had enough vitamin A in your diet?