[Solving The Puzzle]
The group as whole represents "that Catherine is a woman of many angles & dimensions". The second meaning is equilibrium.
The Classical pose photos "depicts Catherine's intention of remaining loyal to traditions".
The Red Dress photo "she's depicting her mission as an ambassador of the Royal Family in modern times".
The Close-up photo "represents her character & personality". The choice of a soft blurry close-up is deliberate becase a "high contrast, crisp color photo could have been too self centered for Kate's personality".