The ghost can only take one form at a time; however, that form doesn't have to be as the deceased person looked as they died, though that's certainly up to your discretion! Bear in mind, though, that the ghosts are trying to help, and not traumatize your character, so they certainly won't take the form of, like, someone who's been cut in half in a freak accident or something (unless they appear as they did before the bisection!!)

Long story short, they won't be looking gory or unnecessarily horrifying beyond, y'know, having a dead person's appearance, but anything past that is totally at your discretion!