Just a note, nothing final; a few comments.
Sometimes the nymphs seem to me as spirits that operate on various levels of reality. In a few images they seem to be creating weather: rain, wind, snow, rainbows.
A shot in the dark: If the author was a madman, maybe he saw his mother naked in the bath once, and her image populated his visions.
A strange detail that hasn't been noted in commentary that I've read on the VMs: many of the nymphs hold their arms behind their bodies in positions that would be uncomfortable or impossible if they were human.
When they're not bathing in tubs of green liquid, some of the nymphs stand in vehicles that look like hovering Segways.