I see two options. I think a dwemer black reach home would be super cool and be the perfect home. On top of that lots of furnishings already exist on top of what could be added with it and for it so it has lots of potential for decorating. The second option is to make a second vampire home in blackreach and use it as an excuse to add even more vampire furniture because right now there is too little bad guy furniture in game. Looking at all the decorations about 80% of them are only suitable for "good guy" style homes and anyone who wants to make a bad guy home is very very limited in what they have access too.
For a vampire home the lack of anything blood related is hilarious. No blood splotches or patterns, no dried blood or fresh blood pools to put under tables. I want to like these evil homes but it feels like there is just no way to furnish them and make them interesting right now. I hope Zenimax sees this and takes it to heart. I know the good guy players will moan for a year but if they looked at the big picture they would see how much of a discrepancy there is.