The skin ranking system is as follows:
The Council - As Jedi Masters the Council are free to use other skins, but usually they use either the Luke Skywalker skin or the Jedi skin. If they have apprentices their skin is different (see Jedi Trainers below).
Jedi Trainers - As Jedi with apprentices the Jedi Trainers use the jedi trainer skin.
Jedi Knights - As being ranked with the power of the Jedi, the Jedi Knights use the Jedi skin.
Padawan - As learners who have not yet earned the rank of Jedi, the Padawan are free to use which ever skin they choose, however, their skin will reflect on the side of the Force they choose, so choose wisely.
Sith Lord - Izzeh is free to use either the Luke Skywalker skin or a Dark Side skin.