Anyway, these gods were (Chinese, then Japanese names):
Qīnglóng — Seiryū (The Azure Dragon, representing Spring and Wood) to the East;
Zhūquè — Suzaku (The Vermillion Bird, representing Summer and Fire) to the South;
Báihǔ — Byakko (The White Tiger, representing Autumn and Metal) to the West;
Xuánwǔ — Genbu (The Black Turtle, representing Winter and Water) to the North;
Huánglóng — Kōryū or Ōryū (The Yellow Dragon, representing the Changing Seasons and Earth) to the Center;
the 5th one rarely appears .
So as you can see:
The Azure Dragon - would have been Byakuya, since wood can be associate with trees and trees with sakura petals;
The Vermilion Bird - would have been Ichigo, since it is suggested that he might have a flame element, beside he already once stopped the phoenix spear;
The White Tiger - would have been Renji (his new clothes even have tiger straps), since his shikai is Zabimaru - Steel Snake, thus associated with metal;
The Black Turtle - would have been Rukia, since her element is ice and the turtle is associated with winter and water;
The Yellow Dragon - if it would have appeared - would probably be Ganju, since he was the only one to showcase a great potential and capabilities in wielding the earth element.
Also, sometimes they are also associated with certain traits and colors, like:
Dragon - Blue - Bravery (symbolizing Byakuya eventually overcoming The Fear Quincy ?),
Phoenix - Red - Kindness (Ichigo showed it multiple times),
Tiger - Green - Strength (yep pretty much Renji, especially the strength of his resolve and will),
Turtle - Violet - Versatility (I guess she can use her Zan, Attack Magic, Defense Magic, Trap Magic and Healing Magic and the like ?).