Creating a Testimonials Content Type and making it work as it should
You can give anonymous users the permission to create content of that type. And you can set the default publishing setting to unpublished (They can't change that unless they have the required permission).

For the theming part, if you are using the admin theme for the node add/edit forms, then you'll have to disable it for that content type. You can do so with a bit of custom code and implement hook_admin_paths() and return 'node/add/content-type' =&gt; FALSE path. This will override the definition in node_admin_paths(). Because for a path to be considered as an admin path, there needs to be an entry that returns TRUE and no entry that returns FALSE.