This function had been marked as deprecated since 3.4.0. Use add_theme_support('custom-background, $args)

Add callbacks for background image display.

Signature

add_custom_background( $wp_head_callback = '', $admin_head_callback = '', $admin_preview_callback = '' )
wp_head_callback
 (callback) Call on 'wp_head' action.
Default: ''
admin_head_callback
 (callback) Call on custom background administration screen.
Default: ''
admin_preview_callback
 (callback) Output a custom background image div on the custom background administration screen. Optional.
Default: ''

Return

(void)

Source

function add_custom_background( $wp_head_callback = '', $admin_head_callback = '', $admin_preview_callback = '' ) {
	_deprecated_function( __FUNCTION__, '3.4', 'add_theme_support( \'custom-background\', $args )' );
	$args = array();
	if ( $wp_head_callback )
		$args['wp-head-callback'] = $wp_head_callback;
	if ( $admin_head_callback )
		$args['admin-head-callback'] = $admin_head_callback;
	if ( $admin_preview_callback )
		$args['admin-preview-callback'] = $admin_preview_callback;
	return add_theme_support( 'custom-background', $args );
}
WP Trac GitHub

Link here