Boss Pro: Home Page Overview
The Boss Pro theme displays a fully widgetized home page which is broken up into 7 widget areas.
Three of the widget areas display background images. You can keep the default images in place, or update with your own images.
To replace the existing background images, go to Dashboard > Appearance > Customize > Front Page Images. Select Remove to completely remove the background image, or Change Image to navigate to your media library to locate a replacement image. Once you have chosen a replacement image, click Save and Publish.
The recommended image size for each of the background images is 1600px by 1050px.