Something like me
couldn't be used by a robot unless it was coded to detect that specific image, or it had some kind of OCR...
The important thing is not to make it a link, because if you do this:
code:
[email=spam@shoutbox.menthix.net][img]http://guillaumelforum.theglassprison.net/gmail.png[/img][/email]
Then the robots can simply get the address from the HTML link code (<a href="mailto:...">).