... would do a lot to bring some life to these character created environments. One per room would be plenty.
Other things that would help to decrease the "sterility" and lackluster empty feeling of these spaces would be characters that were actually doing something other than just standing there (dancers and medical personnel being the notable and very welcome exceptions). Aside from dancers, most placable personnel for strongholds might as well be paintings or wax statues. They wouldn't have to move back and forth, simple "in place" animations could add a lot to the tableau, such as:
<> working at a computer
<> engaging in an animated conversation
<> playing an instrument
<> entering data on a hand tablet/computer
<> fidgeting while standing (guards)
<> sweeping the floor
<> etc.
Any of these simple animated NPC personnel (particularly if combined with a few select ambient sounds like office chatter, medical devices, hotel lobby noise, cantina music, workshop or garage noises, etc.) would add a lot of life to the strongholds some of us spend so much time crafting.