Basically when you attach a PNG image as the Vendor Image, it is not rendered in the preview invoice image.
Yes, this is not a bug, it is a restriction of tcpdf. Just use proper pngs or jpg.
Thanks Milbo!
:)
Btw, do you need help regarding Marketing/Documentation? ;)
We need always people who are eager to extend docs.virtuemart.net. Marketing is always welcome.