Would be great if Scrivener offered inline (insert) text box and (insert) image well functionality. This would be especially helpful for template documents.
Page layout tasks like this are outside of Scrivener’s scope.
I don’t know if you are a fan of LaTeX, but there are a few resources for inline text boxes and inline images et al. available via LaTeX.
A few resources for text boxes, inline or otherwise, include:
Although the ‘wikibooks’ site is marked as “may need to be updated to reflect current knowledge”, the site can provide you with an idea of what is available.
As for inline images, one useful reference (including a sample of what an inline image would look like) using the adjustbox LaTeX package is available at:
The full LaTeX library (with over 6,000 packages) is of course available on CTAN at: