Learn English – What do you call a flexible diving platform

I think the term you might be looking for is 'taxidermy mounts'.

Taxidermy is the preserving of an animal's body for the purpose of being put on display. A person who creates these displays is called a 'taxidermist'. The end result is called a 'taxidermy mount' or just simply 'taxidermy'. There are different methods used in taxidermy such as overlaying the animal's skin over a frame of wood and wire and then stuffing it with cotton, creating replicas with resin or fiber glass, or freeze drying the whole animal and removing its organs.

Preserving chemicals are sometimes applied to the skin used, or the skin is tanned, which is why they do not rot over time.

Such a person is called an extra (or background actor).

From Wikipedia:

A background actor or extra is a performer in a film, television show, stage, musical, opera or ballet production, who appears in a nonspeaking or nonsinging (silent) capacity, usually in the background (for example, in an audience or busy street scene). War films and epic films often employ background actors in large numbers: some films have featured hundreds or even thousands of paid background actors as cast members (hence the term "cast of thousands").