The statue in the prison cell is most likely Uinen, which page incidentally tells us
Two explanations exist for the name Uinen. In The Etymologies, the first element came from a root UY-. Several other words under this lemma mean "seaweed", though the name Uinen itself is not explained.
and we see seaweed sculpted in her hair. In the published Silmarillion we also have that her
hair lies spread through all waters under sky
and the statue's hair is very long, going all the way to the water.
The big statue with outstretched hand is Eärendil, with the silmaril on his brow, and the bird just by his right shoulder is representative of Elwing when she was turned into a bird. And the hand gesture is in fact consistent with the Elvish welcome gesture described in Nature of Middle-earth, while the Argonath statues are giving the sign of warning and rejection.
Edit: The showrunners confirmed in the official show podcast (Ep 3) that it was indeed Uinen in the prison, confirmed again that it was Eärendil with the Silmaril and Elwing in the harbour. And, incidentally, that the small bust statue next to Elendil in Ep 3 when he is talking with Galadriel is the Valier Nienna: