[Plugin: Admin Customization] Inquiry about planned features

I’m not planning to add suport for modifying styles. Than can easily be accomplished by hooking the page head and adding your own styles.

For example, to modify the login form background color you could write:

add_action( 'login_head', 'my_custom_form' );
function my_custom_form() {
?>
<style type="text/css">
    #loginform {
        background-color: #eee;
    }
</style>
<?php
}