Actually according to the original lore leaked by someone who worked for bungie (rumoured) the traveler is actually both the light and the darkness, sort of a yin and yang if you will. So in pre release concept art said before by another guardian(Eurofukanagaxxx), the inside of the traveler looks a lot like The Black Garden. So maybe the inside of the traveler is actually something similar. A lot of speculation has been made that the traveler is connected to the Vex. It would be nice if we had a full story and not just tiny patches of one.