Thumbs in list manage_pages_columns manage_posts_columns
add_filter('manage_posts_columns', 'featured_image_add_column');
add_filter('manage_pages_columns', 'featured_image_add_column');
function featured_image_add_column($columns)
{
$columns['featured_image'] = 'Featured Image';
return $columns;
}
add_action('manage_posts_custom_column', 'featured_image_render_post_columns', 10, 2);
function featured_image_render_post_columns($column_name, $id)
{
if($column_name == 'featured_image')
{
$thumb = get_the_post_thumbnail( $id, array(50,50) );
if($thumb) { echo $thumb; }
}
}