From Shaiya Wiki
When you first build your character, you will have various options in terms of height, hair color and styles, faces, gender, and character classes.
Union of Fury: http://www.youtube.com/watch?v=McU6l602OKc
Basically, for Vails Pagans and Oracles look the same in the beginning, while Assassins have a more original look. For Deatheaters (or the Nordein originally), Hunters retain a unique look while Warriors and Guardians look the same at first.
Alliance of Light: http://www.youtube.com/watch?v=TikKJ_k9-XU&NR=1
For Elves, their Mages have a unique appearance, and the Rangers and Archers look similar. For Humans, Fighters and Defenders look almost identical, and Priests look different.
Depending on your class, that will determine the clothing you wear. Additionally, if you want to change your character's gender, hairstyle, face, and so forth, you can purchase an Appearance Change Scroll from the Item Mall (whether while you're playing the game, or on the Aeriagames website). But, what really makes this scroll special is the fact that it offers you more options in terms of altering your looks. So, if you're distraught by the fact that someone else has the exact same look as your character (and trust me: I know what that's like), you can give your character a truly unique look.