This game does not have 'real' face mods. You can use better textures, or some 'hot' head meshes, but that's all. You should make your face by tweaking Fecegen slider, and the result can be often terrible. You can start with generating random face, then tweaking it to get desired face, or if you're impatient, you can copy someone else's saved face to your save file. Or maybe, you can use
SI Facegen Modeller for making a face you like(Still you have to work with these crazy sliders, but it's better than in-game face making).