You will need to add the img tag to the list of allowed HTML (in config.php).
The img tag is not allowed by default as there's the risk of it being misused to link to Javascripts (or other scripts) which could be used to do all sorts of nasty things. So you should only allow that tag for admins but not for normal users.
Or you could download that image and upload it on your own site, using Geeklog's [ image ] pseudo-tag.
bye, Dirk
