Add featured image

gistfile1.php

//* Add featured image
add_action ( 'genesis_entry_header', 'jds_featured_image', 15);
function jds_featured_image() {
  if ( is_single() )
    return;
  if ($image = genesis_get_image('format=url&size=thumbnail')) {
  echo '<div class="alignleft">';
  printf('<a href="%s"><img class="alignleft" src="%s" alt="%s" /></a>', get_permalink(), $image, the_title_attribute('echo=0'));
  echo '</div>';
  }
}