I'll start with an example.
http://www.phpbb.com/styles/db/index.php?i=misc&mode=display&contrib_id=3153
Click on the link of 'phpBB version: 2.0.23'
It will take you to http://www.phpbb.com/styles/db/index.php?i=browse&mode=group:phpbb&sub=2.0.23 showing 2.x styles.
There also isn't any search option available to find styles for 2.0.23 or the most recent 3.x version.