Here's a bunch of info about what you can do with background images:
http://www.css3.info/preview/background-size/
Since the site itself isn't responsive, it won't do any good to try and make just that one element responsive. Check out what happens when you give your image 100% width and auto height.

Another book recommendation:
http://www.sitepoint.com/books/htmlcss1/
and a free download:
http://it-ebooks.info/book/1549/
Responsive design will be quite the uphill battle if you don't have a good understanding of CSS3/HTML5. A few hours study will will go a long way.

https://www.callendales.com