I can actually tell you that 100 items for a small cottage is too low if you're like me & make some awesome furnishing combos (such as setting a royal partition inside a half-partition or putting a tabletop lamp under each corner of a canopy bed & having the lights in the house low/off). And considering the vast difference in floor space between small & large, 200 items for a mansion is drastically underestimating the interior decorators of the game (especially when you consider just how much housing stuff they've added to the game since housing was first implemented).