I am not a code expert or anything but I have changed my header on each page by not using the default header image. I chose an image to be my header image and also added various other pics I want on different pages. Then on each page when it has a link at the bottom called “Featured Image” I chose a separate image then. I had to save it first then load/update it page by page. I picked the image from my gallery of images. If you try to add the image on the featured image w/out saving it as a header image, you can’t edit it. If you save multiple images on the header page, you can edit them there. Hope this makes sense. Get in there and play with it, and it will become clear