Most people find it hard to make a theme that actualy checks if the visiter is a member or visiter. Most people thinks it's is_user_logged_in but it's not.
Instead add this code to your functions.php
<?php function user_regvis_message() {
get_currentuserinfo() ;
global $user_level;
if ($user_level > 0) {
echo "Wellcome visiter"
} else {
echo "Wellcome Member"
}
}; ?>
then add this in any location of your theme
<?php user_regvis_message(); ?>
Quick note; if your including tags do not use echo instead just place the code the fuction dose if for you