I guess we're talking about Drow dwelling underground here.
One big problem with this is that space is at a premium. There are no large amounts land filled largely with air and nothing else available. You'll have to get a cavern and build there.
So you'd expect similarities between drow architecture and dwarven architecture, but that's not true, mainly because the drow will not sink so low. They may be depraved, evil dark elves, but they're still elves, with an appreciation for beauty for beauty's sake, and for elegance. And since they're very fond of magic, they'll incorporate it into their architecture:
Imagine a cavern where every surface is used. Not only the floor, but also the walls and ceiling. They'll hollow out stalactites - and stalacmites - to build their homes in. Especially the more powerful noble houses will own these buildings, so expect them to be heavily guarded.
The houses will be decorated in both mundane and magical manner - elaborate sculptures as well as magical displays - and of course both might and will contain deadly defenses.
The edifices will be walled, of course, with mundane walls, magical defenses, or sticky spiderwebs, but also patrolled against flying attackers or lizard cavalry (the drow liding lizards are able to walk along walls anc ceilings, so walls will be along walls and ceilings as well as on the ground.
The interiour will also contain lots of ornamentation, again both mundane and magical, and again you'll have to expect traps and hidden defenders.
The scarcity of building space is always within the drow's minds, but expecially the more powerful noble hauses will make a point of "wasting space" to purely ornamental installations to show that they can. That, again, some of this space will actually be used for defense. Also, the drow will use their aptitude for magic towards this problem, too. Expect many houses to be larger on the inside than out, with some or all of it being within extradimensional spaces.
They will also dig out more space (or, more precisely, let slaves do it), but they will also use magic to excavate and secure space. It's not that unlikely that they will have beholder slaves to do the digging, and use magic to strengthen tunnels and excavations.
What else?) I'm am very curious about their doors and windows, light fixtures, seating, pillars, etc. And do they have weird rooms surface peoples wouldn't have? (We have "sun rooms" and "flower gardens," things that makes no sense for a dark elf) Any good pics or discrips would be appreciated.
