If you open a free account with the likes of flickr
https://www.flickr.com/, or Photobucket
http://www.photobucket.com You can just copy the link to your picture (once uploaded on their webspace) & paste it into the message on here.
Alternatively, if you want to do it off, say, your Facebook account. Right click on the Facebook picture, click on "View Image info", copy the "Image info", then paste into the thread on here via the "insert image" link on top of the thread box. (Looks like a picture)
Hope that helps
