I think some might argue that face is Katara's mother, or something crazy like that, but it's impossible. Blue eyes run in the tribe.
As far as the statue... I dunno. I mean, I'm no Catholic, so I'm not familiar with the whole Mary thing, but the Wiki article does say this:
Quote:
The term "pieta" originated from a custom of the Roman Empire around the time of AD 64, referring to the act of prostrating oneself, and putting forth an "Emotion...of great love accompanied with revering fear....of the [Roman] Gods."
Weeeell, that could be applicable, depending on your view of things. True, Katara has great love for Aang, and vice versa, and Aang is something of a god, but the only thing that puts me off that is the fear part. Katara doesn't fear Aang. In The Desert, she was the only one who didn't run away. As far as reverence, she doesn't revere him... they're equals. Well, not power-wise, but in their relationship, they're equals.
I think they're both just coincidences.