Affected by location of the hearthfire, maybe somewhat by location of the character. Influenced by proximity to corpses, graves, trash piles, hides, flowers, beds, furniture and artwork (taking their quality as multiplier), as well as types of tiles (dirt, stone, metal) and items (diversity of runestone collections, wall hides), and whether the hf is within fence, palisade, wall, village and kingdom claim, and how many other hfs are around it.
The effect could be a penalty/bonus to all stats and skills, like -25%/+25%. Maybe specific bonuses could be tied to specific props, like combat skills to the amount of skull poles around the hf, and psyche to the amount of artwork.
The idea behind this is to encourage people to decorate their villages (or at least a practical reason to do so), expand more due to need of specially decorated rooms, increase production and grind of useless items like art and furniture, and make more places like these:
