I have images (.png) set as background images for templates. When I complete the book and publish for Responsive HTML, the cover page that contains the background images do not display. I verified that "Use Distiller to create images" is not checked in my Publish Settings-Style Mapping-Image Settings. The document is Unstructured, if that matters. Thank you for your time and assistance.
What I can think of:
Move your background graphic to the reference pages and give it a name. See here for more explanations: https://www.rockymountaintraining.com/adobe-framemaker-more-on-reference-pages/
In the paragraph designer create a new paragraph. In the Advanced Settings set this graphic in Frame Below or Above.
Then on the body page extend the main text frame to the edges of your page and apply the new paragraph format to the first paragraph on this page.
In the Publish settings in the Style Mapping tab go to the Image Settings. Activate "Import Reference Page Images".
Then your background image should be on your HTML page.
html5 output uses only your body page text flow. To display your image you will need to rebuild your cover content within the floW on the body page. If the graphic is truly a background image and isn’t content, then you could use css to display it.
This is one of the reasons I never place content onto master pages.
Let me know if you need more detail.
Another option is to put the cover page image into an anchored frame as the first line in you body page flow. In order to handle output to both print and HTML5, you can make this part of the text conditional. An easy way to handle this situation is to rasterize the cover page from a pdf version of you document. Export the rasterised image to png and the insert it, as I have just described.