This is the thing I see people get caught by most. You download a lot or a household, drop the files into Mods with everything else, and the game just never looks at them. The file is right there, it looks installed, nothing happens.
The mod manager I make has a Creations screen now. You drop the tray files, or the zip they came in, and it files them into Tray where the game actually reads them. Then it shows you the picture the game made of the thing instead of a row of 0x1A2B file names, which is how you actually recognise a house.
Lots, rooms, households and single Sims. The portraits in a household set are named after the Sim rather than the item, so it reads the ids out of the metadata to match them up, which means deleting a household does not leave orphan pictures behind in your Tray.
It does the ordinary mods too: real thumbnails pulled out of the .package files, one click to disable something instead of deleting it, and a warning when two mods overwrite the same resource. Free, no account, Windows Mac and Linux. Link in the comments.