I could not get your question exactly. Are you referring to the possible values in $new->data ?
For eg:
Code
$new->data['admin_email'] = 'admin@domain.com';
If you want to provide the Site Name for a particular script you can use:
Code
$new->data['site_name'] = 'My Custom Sitename';
You can find the possible values for a particular script in the install.xml of that script. For the above example we got the "site_name" from the following code in install.xml