The easiest way to post pics from a picasa web album is simply to right click on the image in IE and select "properties." In the window that opens up you'll find next to "Location" the image URL. Just highlight and copy that, than paste it into your post between the image tags, as normal.

Another way to do it is to click on "Link to this photo" in the right menu of the web album page. Once that opens up, you can select the size image you want (thumbnail, small, medium, large), make sure the "Image Only (no link)" box is checked, and then highlight and copy the URL that appears in the "Embed Image" field. Again, you can then just paste that between two image tags here in your X Marks post.

Enjoy Scotland!