Think about what's in the room above your heirlooms, too. Heat causes damage. Don't hang valuable objects over radiators, heat-producing appliances, or the fireplace. Books you want to read twenty years from now shouldn't be shelved on the mantel, the windowsill, or the radiator.
Light causes fading and other damage.
Don't put valuable books and paper where they'll get direct sun or bright light of any kind. Hallways or other rooms without windows are best. Install and use shades and heavy curtains where you can't avoid windows. The glass or plastic glazing of a frame will keep pollutants and dirt away, and handling or tacks will not damage edges. Video, color slides, and most color prints have a limited life expectancy.