How can one repent from sending a girl's picture to a foreign young man, and get rid of feelings of guilt, remorse, and fear of scandal?

You have done well to become aware and to awaken your conscience. You must perform sincere repentance, which expiates sins and transforms evil deeds into good ones, as Allah Almighty says: "Except for those who repent, believe and do righteous deeds. For them Allah will replace their evil deeds with good ones. And ever is Allah Forgiving and Merciful." To get rid of the pangs of conscience, realize the greatness of Allah's forgiveness and have a good opinion of Him, for He is the One who said: "But indeed, I am Forgiving to whoever repents, believes, and does righteousness, and then is guided." Strive to combat the fear of scandal by turning to Allah and asking Him for concealment and well-being.