Hi,
The template for the frontend is in the root directory /templates. If you want to create one by yourself, you can duplicate one (from default or glass_gray directory) and change any data in the template.php file.
For example, imagine you have a new directory mytemplate, you will have to modify these lines in the file template.php:
class osC_Template_mytemplate extends osC_TemplateInfo {
var $_id,
$_title = 'MyTemplate',
$_code = 'mytemplate',
$_author_name = 'Helgvor STOLL',
$_author_www = '
www.mywebsite.fr',
$_markup_version = 'XHTML 1.0 Transitional',
$_css_based = '1', /* 0=No; 1=Yes */
$_medium = 'Screen,
...........
So, you will see mytemplate in the templates list in the backoffice and you can so start it (green button) and select it as default. Don't forget to flush your cache browser to be sure.
I didn't verify but for the backoffice, it's totally independant as the template is in the directory /admin (you can rename it for securities issue).
Hope I answered to your question.
Helgvor STOLL
www.delphine-lingerie.fr