This is how to include jQuery Backstretch in a Genesis by StudioPress child theme: 1. Copy the following gist to your functions.php file. 2. Replace "themename" with the name of your theme.

Backstretch For Genesis

//* Load Backstretch script and prepare images for loading
add_action( 'wp_enqueue_scripts', 'themename_enqueue_scripts' );
function themename_enqueue_scripts() {

  // Load scripts only if custom background is being used
	if ( ! get_background_image() )
		return;

	wp_enqueue_script( 'themename-backstretch', get_bloginfo( 'stylesheet_directory' ) . '/js/backstretch.js', array( 'jquery' ), '1.0.0' );
	wp_enqueue_script( 'themename-backstretch-set', get_bloginfo('stylesheet_directory').'/js/backstretch-set.js' , array( 'jquery', 'converge-backstretch' ), '1.0.0' );

	wp_localize_script( 'themename-backstretch-set', 'BackStretchImg', array( 'src' => get_background_image() ) );

}