Instead of downloading a ready-made template or creating your own template from the ground up, there's also a third option—using a template framework. A framework is basically a template with a huge amount of built-in options, allowing you to define the layout, module positions, menu styles, colors, fonts and sometimes much more straight away from the template control panel. Although template frameworks come packed with features and give you a great deal of control , they do require you to spend some time getting to know your way around and learning how to customize them (as different framework developers follow their own specific design strategies).
If you are interested in template frameworks for Joomla, this is a good introduction on the subject: 'Using a Joomla Template Framework to Design your Site', http://magazine.joomla.org/issues/issue-oct-2012/item/891-using-a-joomla-template-framework-to-design-your-site. For a comparision...