Hi
Yes you can use flickr or imageshack and follow the same instructions but paste the url rather than uploading the file:
1. Compose message as normal
2. Select "options" from the tab
3. Under file attachment select "Add/Update"
4. Enter the URL where an existing file resides.
OR
1. Compose mesage as normal
2. Select the image icon from the formatting palette
3. Enter url
Van