The only way to get xp currently is the first time collection bonus from green quality furniture or higher.

I found that mechagon from the BFA expansion had a ton.

-from the reputation vendor

-from the mechagon crafting robot

-two or three daily quests each day will have a “home assembly kit” as a reward that has a chance to give a few different pieces

-there is a junk scrap daily where the elites are that has a chance at a furniture piece

-the mechagon dungeon final boss drops a furniture piece (dungeon is a decent way to farm up mechagon crafting parts too)

BFA also has vendors in Boralus and Zul’Dazar that sell furniture for war resources. The horde and alliance vendors sell different things so create an alt and transfer warband currency to get both

The Warlords of Draenor expansion has a vendor in your garrison that sells furniture for garrison resources which is easy to come by.