You can achieve this by getting the Membership Level of the current user, and making a conditional based on this. As I do not have a license for wishlist member, this is untested.
I suppose $member_id
to be the same value as the WordPress ID of the logged in User.
<?php
global $current_user;
get_currentuserinfo();
$member_id = $current_user->ID;
include('wlmapiclass.php');
$api = new wlmapiclass('http://yourblog.com/', 'yourAPIKey');
$api->return_format="php"; // <- value can also be xml or json
$membership = $api->get( /members/{$member_id} );
$membership = unserialize( $membership );
print_r( $membership ); // see in which value the actual ID or slug of the membership is stored, I cannot reproduce that..
?>
As TomJNowell pointed out, it would be even better to change the include to
get_header( $membershiplevel );
So you are good to go for future Membership levels.