Prefer a simple, uniform background
A simple background keeps attention on the item.
A clean wall, plain fabric, large sheet of card or lightly textured surface generally works better than a visually busy room.
Pure white is not required. What matters is sufficient separation between the item and the background.
A very light instrument may be easier to read against a slightly darker background, while a dark item needs separation from a dark backdrop.
Avoid strong patterns, highly saturated colours and reflective surfaces that compete with the subject.