Pedestals allow you to display nearly any ingame object. Engraving is also pretty neat, and comes with a lot of flavor text, often historical.

Cages can be used to create zoos too.

I assume you mean modding.

In the past, via the usage of TWBT which changed the sprites for the detailed ascii pixels and non-use decorative workshops existed, like the Masterwork "Decoration Block", which forced a image via the same method every time it was activated with a reaction. Or making materials refer to a particular theme, like Egyptian for sandstone.

Topple's halflings uses similar technology to change the door's to something more race appropriate without having to totally redesign sprites and add new stuff. Its not really possible to add more furniture other than vary pedestals/cabinets, but you can still be creative with how its presented.