Hello Ivan,
you can update the code where the file listing is being generated. Please open up this file:
sdl\base\code\core\managers\fileManager.php

there's a function called listFiles(). Currently on line 170 the '.' and '..' entries are being filtered out from the listing, I suggest it is the right place to add your exceptions there as well. So the final code might look like this:
       
    if( in_array($file, array('.', '..', 'thumbs.db') ) )