Example of membership sign up?
There is the generic CiviCRM demo, but that only shows the back-office part (see https://civicrm.org/demo). I assume your client would be interested in the outside facing web part, and that entitely depends on what you can do with Drupal, Wordpress or Joomla. It will be hard to show you one example that gives you an idea of what the new member sign up looks like not because they are not there but because there are so many!