The Skins page of the administrator menu allows the modification of the site skins and containers, in order to manage their appearance.
It will be possible for you to have a preview of all the skins and containers simply by selecting one of the present headings Skins or Containers in the drop down list: the page will be automatically updated with the new images.

By clicking Preview under every image, another window, which represents a page of the portal  modified with the selected skin or container, will be displayed.