1. Try installing RoundCube (roundcube.net) quite good webmail interface.
2. You can have your own login page. design login form as per your requirement of graphics. in form add
in login.php file add the code as follows
<form method='POST' action='login.php'>
This will redirect to cpanel webmail.
$u = $_POST['username'];
$pw = $_POST['password'];
$port = 2095;
$protocol = 'http://';
$ss="@domain.com";//change domain.com as your actual domain
$un = $u.$ss;
$domain = 'domain.com';//same here
$redirectlocation = $protocol.$domain.':'.$port.'/login/?user='.$un.'&pass='.$pw;
header ("Location: ".$redirectlocation);
3. To create email-ids, delete email-ids or change password or quota of email you have to use cpanel xml api instead always logging to cpanel backend.
I hope this is needful to you.