Your details
Photo
Head and shoulders, plain background. You crop it in the next step and it shows as a circle.
Layout
Preview
Desktop · 640
Phone · 375
Previews use the fonts email apps actually have. What you see here is what recipients get.
Move it into your mail app
Live panel
The photo panel every signature shares. Save re-renders it. Signatures people have already installed pick up the change on their own, because the panel is an image loaded from this server.
Photo