Character sprites are located in romfs/unit/Is it possible to change to texture of character map sprites? I.e. make Azura's hair pink in all her sprites?
Head sprites are in the Head folder, class sprites are in the Body folder, and the Unique folder contains full body sprites for certain people in certain classes (Like Songstress Azura).
Just find the file you need to edit, do be warned that I've yet to successfully get an edited sprite to work, but you're welcome to try.