What is this optical effect called?
On the bottle of Camp Coffee the label showed an Indian servant carrying a tray on which was a bottle of Camp Coffee with a label which showed an Indian servant carrying a tray on which was a bottle of Camp Coffee with a label which showed an Indian servant carrying a tray on which was a bottle of Camp Coffee with a label which showed an Indian servant carrying a tray on which was a bottle of Camp Coffee with a label which showed an Indian servant carrying a tray on which was a bottle of Camp Coffee ad nauseam. What is this optical effect called?
'A repeated montage' would be the simplest way to describe it, but 'montage' is a very general word that describes the assembly of one or more images within an another image.
Royal Baking powder used to have the same thing on cardboard cutout displays in shop windows. You could count six repeat images, one within the other.
The word 'recursive' also keeps coming to mind, but I don't know if it really applies.