The template used to specify the layout of the administrator back end of a Joomla site. The Back-end Template controls the way your website's administrative tasks are presented for controlling management functions by a Joomla! Administrator. These would include common tasks such as: user, menu, article, category, module, component, plugin and template management.
Joomla ships with some basic default admin templates and one can also checkout our attempt at developing Joomla Admin template - JA Admin.
Check out Joomla Admin Template - JA Admin