As we had mentioned, there are plenty of template clubs online that are using T3 to deliver their templates for their customers and clients.
This is a short list of companies that we know are using T3 as their base foundation to deliver awesome mobile responsive websites using Joomla!.
Template Clubs/Shops Using T3
Web Agencies Using T3
Of course there are many more out there that use T3. If you would like to be listed, please leave a comment and we'll add you to the list.