Since there's currently a lot of possibilities on what may happen with cutomization, go crazy on how you want your Senpai to look like!
If I were to make Senpai a male, I would give him the typical black-haired glasses guy look with uniform # 1 or #4 :3
If I were to make Senpai a female, I would make her look like me! ...which is already her default look... (with uniform #2 or #4. I could always add glasses too, but eh)