I'm going to redesign the existing buildings only, because I'm really bad at building from scratch but can relatively easily design interior spaces.
The big one will stay as a huge mansion, but I will let my own vampire Sim live there. Hopefully with a large family later on.
One will be a shop for all sorts of vampire things: Webs (with and without spiders, which I'll treat as pets in my head ^^), wallpapers, outfits, and of course those bird skulls in a jar. And some blood plants if I can get my fangs hands on them.
One will be a bar where the only instrument is an organ. And maybe a violin. I wonder if the game will send a normal Sim or a vampire as the barkeeper there? Either way, after at least two days there will be a vampire serving the drinks, don't worry about that.
And because there are so few lots, it will also be a gym at the same time. Gotta keep your vamps fit for their next snack ;)
The next building will also have two functions, but this time as a library/museum. Including a vampire llama statue at the front of course. I've seen some nice decoration and statues in the trailer, and at least one painting too, so that should be easy to fill. And then there will be bookshelves occasionally to fulfill the library function too.
The last lot will be a cemetery. I know that there is no such lot type, but the gravestone objects (despite being decoration only) will fill the place before the first Sims have died. I hope I'm able to make it look awesome, I never tried to build anything outside except for garden paths :D
I will use the ugliest house for this one but will of course bulldoze the building itself. And I hope that we can use that fog from some parts of the trailer for our houses too, as it would really give my cemetery the "certain something".
Before you ask: Yes, I'll make underground chambers as well. Maybe four or five seperated little "mazes" with some being at level 1 and some level 2. This looks SO awesome in my head right now :D
If there is a premade vampire family living in one of the houses I will of course not use that place. Maybe I'll not give them a bar/gym then, there are no "not modern" training things anyways. And that will give them an incentive to leave their home, even if it's just to go to the bar ^^