You can use any photograph that you want in your facebook account, and some people do not even use a real name, or only part of their name. You can pretty much put as much or as little information as you want on your page, and you can add friends that you like and not add anyone you do not want to see your page. Everything can be kept private, or shared with your facebook friends, or some people make it so anyone can see, it is all up to what each person prefers.
I change my profile picture whenever I feel like it , and often use photos from flowers in my garden. So it is not ever necessary to use a personal photo, and it can be one from your files of you at some earlier time, or of something else completely.