I live in a 56 year old house with a walk out basement that has lots of sunlight.
Four years ago I have done some work on this old house, changed regular doors with metal French Doors, and changed the location of the stairs leading to the basement.
Lately, we can hear loud noises coming from the ceiling and walls. Often I can hear noises from around the new French doors.
Could the heavy French doors be settling??

The doors may be settling but its more likely the whole house is just showing its age. Wooden structures will creak, crackle and pop from time to time as they releave stress and temperatures change, nothing to worry about unless you start getting cracks in the walls.