I am trying to simulate a watermark in the footnote. (I know Excel does not
have the watermark function like Word but you can simulate by loading a
picture into the header, I want to do the exact same but load the pic in the
footnote).

When I add the picture (bitmap) to the footnote, the image is flattened
(i.e. the white area is not transparent, as is expected from a bitmap). When
the exact same image is place in the header, however, the white area is
transparent. Why and can it be fixed so that the same occurs when the picture
is loaded to the footnote?

The reason is the image is quite small and I don't want to create a bitmap
that is the length of an A4 page and use that as the header "watermark" (on
lots of sheets that makes the file size unnecessarily big).