I moved this thread to the Q&A forum.
In your profile, there is a field labelled "Link to off-site avatar." In there, you enter the URL of the picture you want to use.
In the case of Canreef's photo posting software, you have the trim the numbers off the end of the filename. I don't know why the software does that, but anyhow, you just have to edit the question mark and numbers off, and then it will work.
Anyhoo I took the liberty of setting it up for you. I took a guess as to which image you wanted as the avatar.
