Settings (customizer) (category)

background_image()

Outputs the URL of the background image set in the theme settings (in the customizer).

get_background_image()

Gets the URL of the background image set in the theme settings (in the customizer).

has_custom_header()

Checks if an image is set for the theme header, or if a video is set and available for display on the current request page.

is_customize_preview()

Checks whether the site is being previewed in the WordPress Customizer (the visual theme settings page). Conditional tag.