With the generation of new technologies, new ways to abuse them were bound to happen. Shortly before the nanodisaster, urban myth indicates the first of what became called 'Nanoveau hallucinogens' became available. This blood-borne paste (i.e. - non-reproductive nanogen) became a very popular 'party drug' in the vein (pun intended) of LSD and Ecstacy.
The first nanoveau hallucinogen that we have significant records of appears to have been capable of accessing a human's blood stream via skin contact (leaving behind a telltale rash of microscopic lesions which lead to the particular strain's street name, 'Red Rush') and congregating inside the intracranial blood barrier. It apparently (no samples from the time still exist, but as indicated by autopsy and toxicology reports and extrapolations from other data) was able to zero in on activity in the optical center of the brain. After a brief (approx 5 minute from arrival) 'learn' period, it would pseudorandomly replay neural signals for the neuron it chose. In some beings, this cause catastrophic seizures, but in most it provided a 'cool' partial-perceptive replay of previous input. IE - a stop sign might be perceived as a red color on a later object, or an octagonal shape, or having white lettering across the middle, etc.
The more modern versions tend to have onboard databanks of 'artistic' sensory impressions, everything from the bliss-inducing 'White Cloud' to the adrenal-stimulating shock-tactic imagery of 'Splash' to the erotic 'T&A' series of nanoveau hallucinogens.