This is tracked here: https://github.com/headwaymaps/headway/issues/85

It's going to be somewhat tricky because of a few mediocre decisions I made early on in the development process, but if you were up for helping out I'd love to get a bring-your-own-style experience working in Headway. Long-term, I want to add the ability to easily brand Headway and customize it for your own needs without forking it.