alt 1: use absolute src path like http://www.mydomain.com/some_path/my_img.gif
alt 2:
Upload this image to your design/images directory and let ez set the path.
Se the TSCM step-by-steb guide for a introduction to change your design http://ez.no/products/ez_publish_open_source_enterprise_cms/documentation/building_an_ez_publish_site/prerequisits