When I get a new message notification by email, the little image next to the notification does not load (see screenshot). This may be GMail-specific, as GMail proxies images in order to reduce privacy issues with embedded images. The URL to the proxied image produces a 404 on Google's side.
Speculation: Perhaps this is because the image is an SVG, and GMail doesn't support it? That would make it an upstream bug, though a workaround may still be advisable.