Within the avatar_comment_display() function:
echo "<img src='" . $tmp_link . "/avatar/" . $tmp_size . ".png' id='" . $tmp_html_id . "' class='" . $tmp_html_class . "' height='" . $tmp_size . "' width='" . $tmp_size . "'>"
I actually had to put the http:// bit in there to make the url correct.
Thanks,
-drmike