Example of using genesis_get_image with its arguments

add_action( 'genesis_entry_header', 'sk_image', 9 );
/**
 * Outputs image linking to permalink.
 */
function sk_image() {

    $image_args = array(
        'size' => 'custom-square-thumbnail',
        'attr' => array(
            'class' => 'alignleft',
        )
    );

    // Get the featured image HTML.
    $image = genesis_get_image( $image_args );

    echo '<a rel="bookmark" href="'. get_permalink() .'">'. $image .'</a>';

}