Root.Main will make ur upload field to main tab Root.Content.Backround will make u new tab called Background.

Still i can't understand ur extends to EnquiryPage try to extend Page instead (if that works u can change). also don't forget to run /dev/build?flush=all after code changes.

Root.Content.Background is deprecated but Root.Background works! Woohoo!

Thanks for the help Friizu -- I realise that this would work just as well if I had this code on Page.php, however I only want to change background images on landing pages, this is why I've associated it with this page type.

So, for the record, the working code is:

<?php
/**
 * Defines the LandingPage page type
 */
 
class LandingPage extends EnquiryPage {
   static $db = array(
  );   
  static $has_one = array( 
     'Background' => 'Image' 
  );

function getCMSFields() {
		$fields = parent::getCMSFields();
		// add the upload control for the background image to the cms 
		$fields->addFieldToTab("Root.Background", new UploadField('Background'));
		 return $fields;
	}
}

class LandingPage_Controller extends EnquiryPage_Controller {     
}

cheers!!