Chimneys get warm and dry out a painting from the back. Picture lights are a bad idea because they focus on a particular spot on a painting and affect its temperature. Light damage, even natural light, is the worst because it's irreversible. We advise on cellar conditions. Even with wine collections, labels can get damp and ruined, which affects the wine's value.
Fire alarms are a concern.
I always advise smoke detectors rather than heat detectors because smoke can build up long before heat is detectible. Also, some detectors look better aesthetically than others. I've often consulted with architects before renovations so the art is planned for properly. I've visited warehouses before art goes to storage. I've even checked brickwork on houses to guard against weather leaks.