I'll admit my fortresses are incredibly utilitarian in their design, to promote the most efficient workflow, safety and happiness, but i feel that can be an artform of its own.
The whole thing is designed around 2 central staircases, with one in the middle that goes to the surface (surrounded in defenses) and one that goes to the Deeps. Then theres a central square room around those defenses where the wood is kept. Then the fortress has 4 wings each with a purpose. north/south goes the industrial sector, where stone, wood and bone, metal and glass is shaped. The shops are four abreast in the middle with a central avenue, associate stockpiles on the other side to the central avenue, both 1 level above and below. Metal is usually its own sub section.
The organics is on the other side to the industrial sector and has a similar set up, and handles food drink, leather, clothes and soap and the like. I found theres actually very little overlap between the stockpiles of these two, except bone and wood but bone technically can go on either side, and wood is in the middle for easy surface collecting.
On the east/west goes bedrooms, usually large 20 dwarf dormitories with cabinets but sometimes i'll do little apartment complexes.
On the other side goes needful rooms, like a common meeting room, dining room, temple, hospital, jail, rooms for nobles, morgue/graveyard, tavern and associate rooms.
After that it gets a bit freeform. Cisterns and wells i try and design below fortress height, for safeties sake, and prisoner storage/processing is either between the fortress and the first cavern or near the magma cistern for the metal industry, for easy disposal.
The Deeps staircase never goes directly into a cavern. It has staircases that branch off and attach to gatehouses in each cavern from above, so you can shut it off with a hatch. That way you can lose caverns to FB's but keep downward access.