Source: The Great Interpretation of Dreams (Ibn Sirin)
An unknown stranger in a dream may indicate the Angel of Death if he is frightening, or indicate good tidings and goodness if he has a good appearance.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
A stranger may indicate an enemy or a friend depending on his appearance and speech.
Source: Signs in the Science of Expressions (Ibn Shaheen)
A stranger is interpreted as news. If good-looking, it is good news. If ugly, it is bad news.