Try hosting the image on a website like Photobucket.com. Just upload the picture, then copy the "Direct Link" Come here to the forums. click the picture icon on the chat box, then paste that code in.
@Lynsey [Midoki] has special psychic powers to be able to identify that.. Must be why she is on staff..
It looks like you tried to post a link to the attachment of an email - did you email the picture to yourself, and just copy the address off of that? Because that won't work. You have to download the image, and then re-upload it to a website that hosts embeddable images. Bear mentioned photobucket, but I prefer imgur, because it lets you directly copy the url with bbcode tags already around it, so you don't have to deal with adding the tags here (manually or by clicking the image in the formatting bar). Either work though.
Fwiw, photo bucket does that too, just copy and paste the link, not need to add tags or use formatting bar
Great Bear had mentioned clicking the little image icon to paste the link into, so I just assumed there was only a direct link.