EVERY notable house needs more slots. And generally speaking, every house. The larger the house is, the least appropriate the item count is. A small house with 200 items is somewhat fine, a medium with 400 starts to feel tight, a large with 600 is clearly insufficient, a notable with 700 feels almost empty.
I mean, my main home is the Colossal Aldmeri Grotto. I have maxed the ESO+ item count, and I still could pack some more ideas if there was any more room... This thing is roughly the size of Daggerfall. It does feel lively and all, but there are so many more things I could do with it. The ship is only half outfitted. The boats on the cliffs are mostly bare, save for the skooma tavern. There are so many nooks and crannys I could fit with some secrets. I could build a platform at the bottom of the waterfall, and so on...
The item count should be at least 1000 items with ESO+, and ideally, 1000 items WITHOUT it.