This code adds a new widget area after the header on all pages excluding your front page. You can change the conditional tag so the widget
WP Customize
You'll find dozens more tutorials related to the customizer using search.
Tutorials in this archive include code which modifies default or add custom functionality to Genesis child themes.
Add Background Image to Widget Via Customize
This solution creates a front page widget area and enables you to add a background image via the WordPress customizer. Here's the image