Contrast of logos on "new user" certificate image

For sites that use a light-colored site icon, e.g. to display over a dark background, the logo is nearly impossible to read on the automatically-generated “new user tutorial” certificate. (Advanced, too.)

Not sure how hard it would be, but could be nice if said logo were stacked over a circle/square with the site header background color, to get the same contrast as used on the site.