Dynamic parallax in custom content type (draft)

So far, my parallax experimentation has been using first custom blocks and then the basic Article content type, and using the front-page Teaser view mode as the parallax

But then I realised I wanted the parallaxed content to be able to promote different things - from blogs to articles, categories, entire sections or maybe even external (related) websites.  So I thought to create a "promotional" content type - a title, picture, description and a target URL or node when selected.

This threw up a few new challenges...