(Sorry if I am replying incorrectly by replying to all...)

> > If, in the GNU/Linux build, you set x-gtk-use-system-tooltips to nil,
> > does the problem go away?
>
> It does for me.  That is, I'm running GNU/Linux and with
> x-gtk-use-system-tooltips set to t, I don't see the image, but with it
> set to nil, I do.

I can confirm this as well!

On Fri, Mar 13, 2020 at 9:25 AM Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Stephen Berman <stephen.berman@gmx.net>
> > Cc: Dustin Lacewell <dlacewell@gmail.com>,  40047@debbugs.gnu.org
> > Date: Fri, 13 Mar 2020 13:11:31 +0100
> >
> > > If, in the GNU/Linux build, you set x-gtk-use-system-tooltips to nil,
> > > does the problem go away?
> >
> > It does for me.  That is, I'm running GNU/Linux and with
> > x-gtk-use-system-tooltips set to t, I don't see the image, but with it
> > set to nil, I do.
>
> Thanks for testing.  So I guess the problem is that we fail to
> instruct the native tooltips to display the image or use the correct
> dimensions, for some reason, and the problem doesn't exist on Windows
> because we always use our own code for tooltips there.
>
> Patches to fix the native case are welcome.
>