That functionality is already part of each theme of mine. What I’ve done is included the option to use the WordPress custom header or a widget in the banner showcase area instead. If I remember correctly off the top of my head, the WP custom header (found under Appearance >> Header ) only shows for the front page and then the banner widget position is for any page in your site.
I’d like to replace the (currently grey) “header background” (found with this path: Appearance>>Customize>>Colors>>Header Background) into an image or gradient