functions.php

<?php

// Image Size to be used
add_image_size( 'be_header', 960, 180, true );

/**
 * Display header image below navigation
 * 
 */
function be_header_image() {
  // Only run on single posts/pages
  if( !is_singular() )
    return;
  
  // Get image ID, stored as post meta
  $image_id = get_post_meta( get_the_ID(), 'be_header_image', true );
  if( empty( $image_id ) )
    return;
    
  echo '<div class="header-image">' . wp_get_attachment_image( $image_id, 'be_header' ) . '</div>';
}
add_action( 'genesis_after_header', 'be_header_image', 20 );