You can definitely create github pages for each repo, using your own html/css/js. You just need to create a gh-pages branch [1]. If you just want to host a new static site, you can even create a new repo just for that, create a gh-pages branch, then make it the default branch and delete the master branch, leaving you with only the gh-pages content [2].
[1] https://help.github.com/articles/creating-project-pages-manu...
[2] http://24ways.org/2013/get-started-with-github-pages/