The image placeholder is only supported at document scope. It would be better if this feature could be used to insert a logo bar in page header or footer.
The image placeholder code was in fact designed precisely for this kind of purpose: inserting images into places where you ordinarily cannot do so, like Separators fields and below titles in section layouts. We just added it to the editor as well because… why not? It’s certainly not the only scope where it works!
That said, you are right in that it doesn’t work in the header/footer fields. I’ll add a note to see if we can add the capability there. It might be there were technical issues with doing so.
Thanks for your reply. Waiting for good news 
The easiest solution at the moment is to compile without, and add it later in a WYSIWYG app.
If your document contains automatically generated references to other pages, I think you could still get away with it, if you’d insert the exact space needed for your header and/or footer image in the margins:
