It would be great to stick your face, logo, or picture next to every email you send. But the risk from fraudsters is just too high.

To be fair, there's the Face header, but it only supports base64-encoded 48x48 PNG images: http://quimby.gnus.org/circus/face/ It's an improvement on the X-Face header, which is supposed to contain 48x48 bitmaps. Either way, almost no e-mail client supports these headers.