The Internet is full of Bootstrap resources; here are a few:
www.wrapbootstrap.com: You can buy or sell at WrapBootstrap. It is a huge marketplace for premium templates and themes.
www.bootswatch.com: Bootstrap themes are released under the MIT license and maintained by the community on GitHub. Themes are built for the latest version of Bootstrap.
www.startbootstrap.com: Startbootstrap is an easy way to learn and develop Bootstrap, as it contains thousands of starter themes and templates, even for Bootstrap 3.
http://themes.getbootstrap.com: These are the official Bootstrap themes and templates from the creators of Bootstrap and include dashboards, admins, and marketing sites.
Here are a few more resources for Bootstrap, but there are many more. You can surf through these sites and gain some more knowledge about the working and intricacies of Bootstrap: