Room quality is only measured in dwarfbucks right now, which is kind of weird. You can put an artifact statue in a 1x2 bedroom and get it to royal. Also, since mechanisms are worth a lot, levers are apparently all the rage in high dwarf society.
The suggestion is to split up the measure of a room's quality into a few categories. For example:
Artistry: Contributed only by the value of art objects: engravings, statues, decorations of objects
Comfort: I don't know if there are many constructions in game right now that would fit this category, but certainly beds in bedrooms are one. Smoothing would be a huge contributing factor to this, as well as the clutter of the room (objects / walkable tiles). Distance to important areas such as food and water storage also factor into it, as well as the dwarf's other holdings.
Utility: The quality of functional objects relevant to the room's function. So a throne in an office, not in a bedroom. Some objects would increase the utility of all rooms, such as coffers.
Size: Contributed only by the value of the size of the room minus overlap penalties. Mostly a noble demand.
By making the measurements multi-dimensional, it makes room design more interesting, as it is not as simple as sating nobles by building levers from artifact mechanisms. Nobles would make more nuanced demands. While they might want a throne room with opulent artistry, but might only want it to have no-adj comfort. The king would be the hardest to satisfy because they would want royal quality in all dimensions in all their holdings