Most of the furnishing recipes are found out in the world, not from the Master Writ vendor exclusively (which has a very small number of top tier recipes). The vast majority of furnishing recipes (well over a thousand) are found in all sorts of containers throughout the world, and also from things like pickpocketing and murder, certain vendors, humanoid enemies, and some other sources in the game. Also, recipe sourcing is influenced by region so if you are in Eastmarch for example, then you will see more Nord style furniture items recipes, and if you are in Alik'r, you should see more Redguard stuff. You will still find other recipes, but the local culture's recipes will be more common.
Apparently they're out there. I am particularly interested in "certain vendors" and "some other sources".
Favourite NPC: Wine-For-All
Mostly PC-EU , with a lonely little guy on NA.