I'm currently in internship, developping java ee app using jsf 2 as view layer, so I want to know if there is any place to download free jsf or xhtml template ( as free boostrap templates ) instead of developping it by myself.
Welcome to CodeRanch! There's loads of HTML templates available online. Search for HTML templates")
I don't know of anyplace with JSF templates. But you can take a HTML template and replace the tags with JSF tags. This is actually how prototyping often works. Someone makes a HTML/CSS page for the users to review. Once they are happy, it gets converted into the web application.
The place to start is to find out what your requirements are. Ask whomever gave you the task what they want the page to look like. They probably have something in mind and don't want some random HTML template from the internet.