Perhaps you need to provide a little extra instruction about the Featured Image meta box. It doesn’t take much to add your own text to that box:
add_filter( 'admin_post_thumbnail_html', 'add_featured_image_instruction');
function add_featured_image_instruction( $content ) {
return $content .= '<p>The Featured Image is an image that is chosen as the representative image for Posts or Pages. Click the link above to add or change the image for this post. </p>';
}
Customize the information that is displayed on the ‘posts’ page
Adding a column labeled “Thumbnail” (and delete the “Comments” column).
add_filter( 'manage_edit-post_columns', 'set_columns' );
function set_columns($columns) {
$columns['thumbnail'] = 'Thumbnail';
unset( $columns['comments'] );
return $columns;
}
Now we need to tell WordPress what to do with this new “Thumbnail” space. Here, we’re checking for the existence of a featured image and displaying it, or noting that there is no thumbnail.
add_action( 'manage_posts_custom_column', 'fill_columns' );
function fill_columns($column) {
global $post;
switch($column) {
case 'thumbnail' :
if (has_post_thumbnail($post->ID))
echo get_the_post_thumbnail($post->ID, array(50, 50));
else
echo '<em>no thumbnail</em>';
break;
}
}
If you have featured images (formerly post thumbnails) that aren’t named as well as they could be, it’s nice to remove the title attribute so that things like “header-large” don’t appear in the tool tips.
add_filter('post_thumbnail_html', 'remove_feat_img_title');
function remove_feat_img_title($img) {
$img = preg_replace('/title="(.*?)"/','',$img);
return $img;
}