Sauna accessories are where a few hundred dollars leaves your account after the cabin has already taken thousands, so it is worth separating the handful of things a working sauna needs from the long tail of items that exist because they photograph well next to a cedar bench.
The short list you actually need
A bucket and ladle if the heater takes water, a thermometer and hygrometer so you know what the room is doing, a backrest or bench towel because timber gets hot against skin, and a timer you can see. That is a working sauna. Everything on this list is cheap and everything on it gets used every session.
Worth adding once you are using it
A headrest, a duckboard or slatted floor mat to keep feet off a hot or wet base, a proper stone load if the heater came underfilled, and a second set of towels so one is always dry. Lighting you can dim matters more than people expect, because a bright bulb in a small hot room is unpleasant.
What can wait or skip
Aroma oils are pleasant and are a leading cause of damaged heaters when poured neat on stones rather than diluted in the ladle water. Bluetooth speakers rarely survive the heat. Decorative hats and scented wall panels are preference, not equipment. Buy none of it until the cabin has been in use for a month.
Materials and the heat
Anything that lives in the cabin should tolerate repeated heat cycling. Untreated wood, stainless steel and ceramic are fine. Plastics deform, adhesives fail and batteries do badly. Metal fittings that touch skin should be recessed or wooden capped, which is why good buckets have wooden handles and good hardware sits below the bench line.
Questions people ask about sauna accessories
What do you genuinely need on day one?
A bucket and ladle if the heater takes water, a thermometer, a timer and towels. Nothing else is required for a safe and pleasant session.
Can you put essential oils on the stones?
Only diluted in the ladle water, never neat. Neat oil on hot stones can flare and it damages heaters.
Do I need a hygrometer?
It is cheap and useful, because humidity changes how the same temperature feels far more than most owners realise.