Ooh, reading this gave me shivers. I remember some creepy childhood visual/auditory hallucinations, but nothing persistent or vivid like this. I do recall being so overtired at about 7 or 8 that my wallpaper started crawling up and down the wall and I ran crying (see above, re. whiny child) to my mother because it scared me so badly.

Neurologically speaking, our brains take a long time to sort out sensory pathways so I suppose as children we're much more susceptible to a nerve impulse firing down the wrong pathway and triggering a hallucinatory event. I've read that babies under about 6 months literally can't differentiate sensory input - touch, smell, taste, sound, sight all use the same pathways in the brain, so listening to music or watching a picture is literally a psychedelic experience for infants that young. Cool.