Set a fallback featured image based on args

functions.php

<?php
// Paste the code BELOW this line into your child theme functions.

/**
 * Set a fallback featured image based on args
 * 
 * @author Reasons to Use Genesis
 * @link http://reasonstousegenesis.com/default-featured-image/
 */
add_filter( 'genesis_get_image_default_args', 'rtug_fallback_featured_image_args', 10, 2 );
function rtug_fallback_featured_image_args( $defaults, $args ) {
	if ( isset( $args[ 'context' ] ) && 'archive' === $args[ 'context' ] )
		$defaults[ 'fallback' ] = 200; // replace with your attachment ID

	return $defaults;
}