The coffin, the piano and the wheelchair are props
prop (noun) – an object that is used by a performer in a movie or on the stage (in a theatre)
Examples of how you can use prop:
Before the director can start filming the scene, the stagehands need to make sure the pen and papers are on the desk, and that the other props are in their right place.
Are those real guns? Don’t worry, they’re just props that we used in our school play. They’re made of plastic and they can’t fire.
Her job is prop designer. At the moment she’s making fake dinners from papier maché.