Bootstrap framework used by Web Developers & Designers to code there Responsive templates/themes for clients and for their own projects. Bootstrap Themes used to design Mobile Preview Templates/Themes for Responsive view on Mobiles/Tabs and Desktop.
There are tons of Free and Premium themes on internet that based on Bootstrap Framework. Now Nearly every templates designed on Bootstrap by Designers or Developers, Mostly Available in Mockups or PSD’s or even WordPress/Drupal Themes.
Where you can Find Best Premium Bootstrap Themes?
Bootstrap Themes Available nearly in every CMS or simple HTML/Css Codes. You can Find Latest and Popular Designed Templates on ThemeForest.net or you can Hire Designer from Fiverr or Freelancer.
Where you can Find Best Free Bootstrap Themes?
Well you can Google for the Best Themes and Look through Google images for Fastest Preview else wasting your time searching themes.