Interesting that you pick this one; it's not a "glamorous" shot but shows her strength and dignity very clearly.
I love it for a number of reasons, being un-posed, the slight turn of the head, the look in her eyes and the light/shadow that just barely brushes the edges. Love it. Love it.
As an amateur historian of Tsar Nicholas II and his family, HIH Grand Duchess Tatiana was always my favorite. While I was fascinated about the possibility of Anna Anderson actually being HIH Grand Duchess Anastasia (I remember he claims well, she was still alive when I was growing up) I was always enamored of Tatiana's beauty and poise. She had such a regal bearing without being regal, if that makes sense.