Themes usually live in a directory called wp-content.

Determine how the server handles directories which aren't present vs files which aren't present in a path that exists in order to tell which themes are installed.  

use wp_common_theme_files.fuzz.php inside the identified theme dirs 

Often you can tell the current theme by viewing source.

Theme list generated last on Sept 6 2013

from: http://themes.svn.wordpress.org   

