If we want to include a background image/transparency INSIDE the content wrapper of the contact page of Preference . . . would you suggest the use of a plug-in, CSS or to tweak your “extras” code?
Kind of depends on what your contact page will be and include, but for the most part, the image that you plan to use. I would keep it to css and target only the article (page) ID so you can create a custom css with a css background. The Preference demo site has a background image on it’s contact page where I used css for that.