Here's a list of themes I liked when going through drupal's Theme Garden:
http://themegarden.org/drupal6/?q=drupal-hosting&theme=marinelli
http://themegarden.org/drupal6/?q=drupal-hosting&theme=oxidation if we can change the colors
http://themegarden.org/drupal6/?q=drupal-hosting&theme=pluralism if we can add a navbar to the top
http://themegarden.org/drupal6/?q=drupal-hosting&theme=salamander
