If you enjoy knocking around with Bootstrap then Bootswatch is for you. It adds a dozen or soo more themes than normal bootstrap. So it has all the normal bootstrap classes but the colors, borders, shadows, hover and buttons etc are all different.

Crisp, light and sleek bootstrap theme’s

Using a Bootswatch theme is so simple too, you just grab the cdn of the theme you want and use it instead of the vanilla Bootstrap source. Keep inmind you can still add your own cusom css rules and styles. Something i really like about the Bootswatch site is it gives you inspiration to different syles of websites. Some have the dark look whilst others look cheerful, light and trust worthy. Love or hate Bootstrap you still have to admire the designers who did Bootswatch themes.