Display Post attachment image

You need to edit the search results template. See the_post_thumbnail(). Relevanssi doesn’t have anything to do with whether the images are shown or not.

I figured it out. You just need to create a function like this and add it to your functions.php in your child theme.

function attachments_search_the_excerpt( $excerpt ) {
  if ( ! is_search() ) {
  	return $excerpt;
  }
  $id = get_the_ID();
  if ( ! $id ) {
    return $excerpt;
  }
  if(get_post_type($id) != 'attachment') {
  	return $excerpt;
  }

  $caption = wptexturize( get_post($id)->post_excerpt );
  $image_url = wp_get_attachment_image_src( $id , 'full' );
  $thumbnailURL = $image_url[0];
  $image = aq_resize($thumbnailURL, 260, false);
  if(empty($image)) { $image = $thumbnailURL; }

  // compile output with thumbnail image
  $output = "<div id='attachment_{$id}' class='wp-caption aligncenter' >";
  $output .= "<img src='".esc_url($image)."' class='iconhover' style='display:block;'>";
  $output .= "<p class='wp-caption-text'>$caption</p>";
  $output .= "</div>";

  return $output;
}
// hook our function to the filter
add_filter( 'the_excerpt', 'attachments_search_the_excerpt');

Then you have it ??