WordPress at a glance
function is not described

get_background_image() WP 3.0.0

Retrieve background image for custom background.

No Hooks.

Return

String.

Usage

get_background_image();

Code of get background image: wp-includes/theme.php VER 5.1.1

<?php
function get_background_image() {
	return get_theme_mod( 'background_image', get_theme_support( 'custom-background', 'default-image' ) );
}