Here is a solution that will insert the glyph annotation at the beginning of buffer:
(make-annotation (make-glyph '([FORMAT :file FILE] [string :data "fallback-text"])) (point-min) 'text (current-buffer))
Replace ‘FORMAT’ with an unquoted symbol representing the format of
the image (e.g.
Instead of ‘FILE’, use the image file name
You can turn this to a function (that optionally prompts you for a file
name), and inserts the glyph at
(point) instead of