simply make a copy of the used texture and fpe and change texturepath/name there. then edit it in a paint-prog like GIMP (open source freeware) or photoshop, but i dont think you can change textures ingame or load textures/characters into a running game. you would have to place all variations of the character on the map and trigger the one that is chosen, but that would cause a raise of ram-use. should not be a problem when using 3 different versions or male/female, but i wouldnt use more than 3.
how you want to show the character? doing a third-person game? interesting.