How-To: Add Achievement Thumbnail to Admin Page

Paste the code below in the functions.php file of your child theme to add thumbnails of the respective featured image for each achievement to the admin page. Set the $solumn_position variable to the column placement you want the image to appear in.

/* Achievement Admin Featured Image *******************************************/
	add_image_size('admin-list-thumb', 50, 50, false);

	function achievements_admin_thumbnail($columns)
	{
		$column_position = 2; //choose what position you want the categories to be added
		$columns_first = array_slice($columns, 0, $column_position - 1, true );
		$columns_last = array_slice($columns, $column_position - 1, null, true );
		$columns = array_merge(
			$columns_first,
			array('achievement_thumb' => __('Featured')),
			$columns_last
		);

		return $columns;
	}
	add_filter('manage_edit-achievement_columns', 'achievements_admin_thumbnail');

	function achievement_admin_thumbnail_column($column, $id)
	{
		switch ($column)
		{
			case 'achievement_thumb':

				if (function_exists('the_post_thumbnail'))
				{
					echo the_post_thumbnail( 'admin-list-thumb' );
				}
				else
				{
					echo "Thumbnails not supported.";
				}
			break;
		}
	}
	add_action('manage_posts_custom_column', 'achievement_admin_thumbnail_column', 5, 2);

http://wordpress.org/extend/plugins/achievements/