I don't remember if I was the one who said it, but I do usually associate certain sims with certain colours, which are reflected in their clothes and bedrooms, but not necessarily the rest of their house (especially if they don't live alone).
Other than that, style is also important. A family-loving religious grandma obviously isn't going to have blue hair and revealing outfits in her room that looks like a gothic tomb, but rather wear comfortable pullovers and long skirts with floral patterns, her room being filled with old-fashioned wooden furniture and photos of her children and grandchildren. Her twin sister, on the other hand, might be her polar opposite, a femme fatale even as an elder, characterised by leather pants and makeup to look younger, along with a high Charisma skill.
Then there's hobbies. Sims who live alone or with like-minded people (like a group of musicians) will usually have their hobbies displayed in one way or another all over their house, whereas for family homes or apartments shared by people with very different interests, their bedrooms usually consist of the usual stuff (bed, mirror, wardrobe) plus at least one item representing something they like to do in their free time.
