Since Steven Moffat's probably going to commission a new Doctor Who logo when his tenure as showrunner starts, I decided to come up with my own ideas on what that could be:
http://lucasforums.com/picture.php?albumid=326&pictureid=2951)
This includes the Seal of Rassilon, as combined with the Garamond font, is meant to give a bit of an elegant look.
http://lucasforums.com/picture.php?albumid=326&pictureid=2952)
This was mainly meant to give a high tech look to the current logo.
http://lucasforums.com/picture.php?albumid=326&pictureid=2953)
This was modeled off of a logo I saw on DeviantArt, which featured a Cyan aura behind the text, in Arial Black.