It sucks to have large houses but nobody in them. Would be much better if there was an option to add NPCs to the place (far more than the three Assistants we can currently have), and it would be even better if we could customize them via outfits and services (e.g. have a Blacksmith NPC who functioned as a smithing station when interacted with).
I saw someone on the forums suggest guards, I think that's an amazing idea. For Guild Halls, you could decide on a signature look for members of your guild, and make it so the guards are all wearing the appropriate outfit. You could even give them Guild Tabards.
The same individual also suggested "Lusty Argonian Maids". First off, I think that would be amazing, secondly, the whole concept of servants in general just fits with the housing theme, particularly for the larger houses like the Ebonheart Chateau. I think servants with appropriate outfits should be available (either via the Crown Store, or through Master Writs). Not sure what service they'd provide, but we should be able to choose things like race, sex, and clothes for them (e.g. make one of our servants into a Lusty Argonian Maid).
I also think it would be cool to give NPCs in your house custom names. You could have a "captain of the guard" NPC with unique armor, you could even have a head butler, who leads all the other servants. You could even use this to give your guild a figurehead, a Guildmaster NPC, with a unique armor set of his own. A Guild Trader for your house, which would function as a trader for the guild the house owner is the Guildmaster of.
I just think there are tons of things that could be done to make things seem more lively in some of the larger houses, and letting us add our own NPCs seems like a really good feature.
Guildmaster of Spectral Liberty - Xbox One - European Megaserver