Storing variables in a theme outside preprocessing
I'm not sure if that's exactly what you're looking for, but Drupal has the concept of theme settings, which allow to configure a given theme with variables.

See http://www.metaltoad.com/blog/how-add-theme-settings-drupal-7 for a great introduction to them.

And according to theme_get_setting(), you can for example store defaults in your theme's .info file, something like

settings[your_setting] = the_value


Should work.