You can put a banker, a trader and a fence in your house, but it still feels kind of empty/unihabited. Being able to put other NPCs in one's house has been suggested before, but it's not quite the same as being able to put the characters in a house that actually live in it. So my suggestions is the following:
Add a crown store furnishing item that lets you place an NPC version of your player characters in your house. This way the houses would feel like there's actually someone living in there other than the current character. You could have all your characters in your house doing different things, or make them look like they're interacting with each other.
In placement mode it would appear as a dummy, selecting the character whose appearance it should have in a pop-up menu after placement (or just the house configuration menu). So I could for example make it look like my tank or healer, or whatever. If you visit your house with a character you placed in it before, the NPC-Version should be rendered invisible. It should be possible to place multiple dummies like that, but only one of each unique character. Characters that were already placed should disappear from the selection menu. There also doesn't need to be any new model created, since it only needs to reference the appearance of an exisiting character.
Another nice gimmick could be to be able to make these dummies loop different animations or be in specific positions (sitting, sleeping, etc).
As a price I suggest between 2500-5000 crowns, depending on the extent of functionality.
This would also enable people to place "generic" NPCs in their houses by just creating a character for that specific purpose (need more character slots, anyone?).