Add default fallback image in Genesis

functions.php

<?php

/**
 * Set default fallback image
 * Modified from: https://gist.github.com/GaryJones/7070243
 * See: genesis\lib\functions\image.php
 */
add_filter( 'genesis_get_image_default_args', 'prefix_stop_auto_featured_image' );
function prefix_stop_auto_featured_image( $args ) {
	if ( ! isset( $args['context'] ) /*|| 'archive' !== $args['context']*/ )
		return $args;
	$id = '4740';
	$lgd_html = wp_get_attachment_image( $id, $args['size'], false, $args['attr'] );
	list( $lgd_url ) = wp_get_attachment_image_src( $id, $args['size'], false );
	$lgd_fallback = array(
		'url'	=>	$lgd_url,
		'html'	=>	$lgd_html,
		);
	$args['fallback'] = $lgd_fallback;
	return $args;
}