Welcome to the home of development aid for customizing and expanding Material Design Lite. Want to use your own CSS classes with the provided styling? Need a component not provided? Confused by how we name things for contributing back? This is the place to help!
For using your own CSS classes or modifying the existing build check out the customizing docs.
There is something you need, but there isn't a Material Design spec for it. For that, read up on some suggestions for more components.