Mail reformatting signature

I have a signature with a couple lines of text, then a small image dropped in, then a few more lines with contact info. For line breaks, Mail keeps re-formatting the signature. It adds a line break before and after the image where I have not created them. I create the signature, (and "File > Save" if necessary) and when I check back it has changed.

This is highly annoying. Any particular reason does anyone know???
Thx!