Revealing mistake: Whenever you glimpse the inside of the TARDIS from outside, a frontal view reveals a picture of what's inside which has been placed at the back of the box. Sadly, it isn't on the sides. This means that, from the right angle, you can easily tell that it is just a box.
Continuity mistake: Throughout series 5 and series 6, The Doctor's hair style keeps changing sides.
Chosen answer: No, no information is avalible for the identity of the entity.
Repo_Man