Arrr! Furnishing looks to be roughly the last crafting puzzle, as houses and the furnisher's shoppe must be implemented first, which is a ways down The List™ at the moment.

Furnishing, obviously enough, will construct furnature for houses owned by rich [pirates/crews/flags] as storage places, meeting places, and just an area to "hang out." Some furniture may have functional capabilities, (eg. slowing down the decay of clothes, maps, or swords) while other furniture will probably just be for show. It will be the puzzle for the Furnisher. (well, there might be a better name for this shoppe, but we'll see)

Also of note is that all the fine furniture you see in palaces at the moment may require a furnisher to make, leaving your palace barren and boring without additional spending.