panel; scene-panel
General term for a flat panel, often used in construction, machinery, or stage settings. The 'scene-panel' gloss refers to a theatrical flat.
A landscape is painted on the stage panel.
Remove the machine's panel and inspect it.
painted pine-tree backdrop (Noh stage)
Specifically the back wall of a Noh stage, always painted with a stylized pine tree. Symbolically represents a reflection of a tree at the front of the stage.
An old pine tree is painted on the backdrop of the Noh stage.