There are a lot of Joomla templates out there, but I only use the best of the best. In my opinion these are the best places to find premium Joomla templates.
Their templating framework really sucks, makes it a super hassle to edit a Joomla template. However, their templates look good and I'm the go to guy when you need something customized in a YooTheme.
A Joomla Template club, graphic designs are a little plain, but that's what some people like. Again a subscription model based on domains.
A well know template consignment site with paid joomla templates for about $40US on average. Some are bad, but most are good.
The most respected template creator of the Joomla community. Hands down the leading Joomla template maker in the industry.
These templates use the morph framework, again not a fan of template frameworks. They offer both free and premium templates, the catch for the free is you need to login.
These templates use the T3 framework, which I stray away from as they are not required for Joomla sites, but if your working with Drupal or Wordpress it's nice to have. Themes can be purchased for as little as $70 and use a subscription model based on domains and copywrite removal.
People seek for uniqueness and being special. GavickPro was started in 2007. They like to keep their designs current and beautiful. All prices are in euros and subscription plans are based on number of domains you use.