Screen saver settings keep defaulting back to National Geographic Photos
After trying the other "fixes" and nothing worked, I went with what was previously suggested here.  Located the Nat Geo folder (HD>Library>Screen Saver>Default Collections>1-National Geographic) and removed those pictures.  This does require your Administrator Password. Then I moved the pictures I wanted into that folder. This works, but it is not a fix as the Screen Saver still defaults to that folder.