Using the Theme Customizer, we can set a background image or a background color that will be used on all pages/posts/products/projects.
Setting a background color for the entire website
Go to Divi → Theme Customizer
Go to General Settings → Background
Use the Background Color to set a solid color as the background
Setting a background image for the entire website
Go to Divi → Theme Customizer
Go to General Settings → Background
Use the Background Image to set a solid color as the background
Note: For the background color or background image to be visible, and if the Boxed layout is not used, each Section element has to have its background color set to Transparent.
Pro Tip: Setting a website background color or background image will work best if the website layout is set to Boxed Layout in Divi → Theme Customizer → Layout Settings