Your pfp is very important to who you are, it might sound weird,but it's true! It allows people to get a slight idea of who you are and wht your personality is! 

examples:

Shadow pfp - with these pfps you can convey what kind of person you are very easily, you can show that you are a sunshiney person, or... emo? idk how to say it, lol. 

Hogwarts sweater - this shows you are proud of your house, and that you are on HiH for the hp aspect of things. 

Or you can use a faceclaim for your character/oc. It is up to how you want people to see you!