For certain page/post types, we have created a global layout with a default image. To swap out these images (or remove them altogether), just go to Divi > Divi Library and search for "header" layouts. You'll see the following layouts referenced:
- Search Page Header
- 404 Page Header
- Blog Header
Simply open up the layout you wish to change the image for and replace the background image as desired.
the section module settings.