I know the option to turn off/down the main lighting has been brought up, but I just want to add my support for that idea. Every single one of my room designs is based around blocking off the main light so I can have a cozy room and it would be amazing to simply be able to turn it off.
I would also love to see partitions for every type of wallpaper, or the ability to wallpaper partitions. I love the wallpapers but I can't ever use them unless I don't mind the partition walls looking different. I would like to be able to create cohesive smaller areas with partitions without being stuck with the three default wallpapers.
50-100 more item allowances at every level from personal rooms to mansions (probably even more for mansions, they tend to look incredibly empty) would be incredibly helpful. I never have enough slots to place little things on shelves and really make it look lived in.
Also, kudos on the little touches like the adventurer's adyuses and the scattered documents added more recently. As someone who generally prefers a realistic, lived-in looking room, I really appreciate that every new housing item isn't a GIANT FLAMING GARUDA SKULL. Mundane little objects like books, papers, mugs, boxes/crates, spare change, keys, jewelry boxes, schematics, and framed pictures are wonderful.
I would love a sink/washbasin for interior furniture!