Am I missing something here?
To me it seems that
[My image](/Users/pdl/Desktop/img.jpeg) works as well as
<img src="file:///Users/pdl/Library/Mobile Documents/iCloud~com~agiletortoise~Drafts5/Documents/Library/Templates/Graphics/logo.png" width="150" alt="Logo"> in a template with style sheet.
The images does not show up in preview but when you e.g. print the preview to a pdf document.