Need to find that GIF of that commercial with the ultra rich russian guy in his mansion, on his golden couch with a miniature pet giraffe "Opulence - I has it!"
You guys call 3x4 apartments luxury? Those are my base size single-dwarf rooms, in which I stick a bed, table and chair, coffer, and cabinet or two, and engrave the whole thing over (eventually). I usually have a central donut stairwell shaft going from the surface to magma sea, and I fiddle with cavern layer spacing to ensure that I have at least 15 z-levels between surface and the first cavern layer. In the top few floors I build the food production, crafting, dining hall, library, temples etc. but the bottom 10 levels above the cavern form the Dwarven Hive - each level digs out a short hallway N-S-E-W, in a plus sign shape, to accommodate apartments on both sides of the 3-wide halls. Corner rooms are 5x5's, with one corner knocked out to match it with the 3x4 and 4x3 rooms above and beside them. The larger corner rooms are reserved for married couples, and the top 2 levels of the Hive are reserved for noble positions - militia commander / Cap o' th' Guard / militia captains on one level, chief med / manager / broker / bookkeeper and legendary crafters on the next, all peasants below. With 5 rooms per quadrant, 4 of those per level, and 10 levels, you can fit all 200 dwarves' living quarters into that space, with room to spare thanks to marriages and children. Married couples need the extra space, I throw in a bunch of extra beds etc. so the dorfbrats don't just crash out on the floors. Mirror this design around a central axis:
###### # = walls
#TC B# D = Doors
D # B = Beds
#H F# C = Chairs
###### T = Tables
#TC B# H = Coffers/boxes
D # F = Cabinets
#H F#
######
#FB F##########
# C#F B#F B#
# CT# # #
D C# C# C#
#HH #H T#H T#
########D###D##
The Expedition Leader gets an adequate office, but when a Mayor is appointed I start the Throne Room and Royal Quarters - pillared, angled and curved carved walls, vaulted ceilings, gems and ore left in place and smoothed and engraved upon. Separate chambers for the royal dining hall and bedchambers, each complete with personal access to the kitchens and hospital ward, respectively, and all royal rooms adorned with encrusted masterwork furniture and statues, and lots of engravings.