How to display the currently logged in user's details
Create a custom module and add following function.

function login_user_fn(){
   global $user;
   //print_r($user);
   $fid = $user-&gt;picture;
   $file = file_load($fid);
    if($file !=''){

    $user_pic  = theme('user_picture', array('account' =&gt; $user , 'path' =&gt; $file-&gt;uri,));

    return ('Hello '.$user-&gt;name.'&lt;br/&gt;'.$user_pic);
  }
}


And than call custom function " login_user_fn()" in our drupal custom block body.