discourse/app/assets/javascripts/admin/templates/customize.js.handlebars

<div class='admin-controls'>
  <div class='span15'>
    <ul class="nav nav-pills">
      <li>{{#link-to 'adminCustomize.colors'}}{{i18n admin.customize.colors.title}}{{/link-to}}</li>
      <li>{{#link-to 'adminCustomize.css_html'}}{{i18n admin.customize.css_html.title}}{{/link-to}}</li>
    </ul>
  </div>
</div>

<div class="admin-container">
  {{outlet}}
</div>