Hi,
thanks for the swift response. Adding a custom stylesheet to the login page is not a problem for me and I did just do so but since White Label focusses on adding a background to the login page I actually was quite surprised to find out it did not had any options for defining how the selected background should be displayed. Hence my question.
Wouldn’t it make sense to add such a setting, just like regular Pro backgrounds, like this:

Perhaps that could be noted as a feature request?
For further reference, it is solvable for anyone with a child-theme.
In functions.php you should add the following:
function yourslug_login_stylesheet() {
wp_enqueue_style( 'yourslug-login', get_stylesheet_directory_uri() . '/style-login.css' );
}
add_action( 'login_enqueue_scripts', 'yourslug_login_stylesheet' );
Then create a style-login.css file in the root of your child theme. In this file add the following:
body.login{
background-repeat: repeat!important;
}