From NY Times: Facebook allows you to designate a friend or family member as a “legacy contact.” If you want to have your account memorialized after you die, this person basically serves as the executor of your Facebook account by managing your profile and can update your cover photo and profile photo, post information and accept new friend requests. (Memorialized accounts without legacy contacts cannot be changed.)
From NY Times: You’ve probably thought about what will happen to your finances, your possessions and maybe even your real estate when you die. But what about your Facebook account? Or your hard-drive backups?