All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
  is His slave and Messenger. 
This Hadeeth was reported by Ibn Hibbaan in his Saheeh and by Abu Ya’ala in his Musnad on the authority of Ibn Mas’ood 
  that the Prophet 
  said: “O Allaah, You beautified my body, so do beautify my character.” Al-Albaani 
  said that it is a Saheeh (sound) Hadeeth. 
However, this supplication is not restricted to when looking at the mirror according to the religious texts that we have come across. Nonetheless, this was mentioned in a Hadeeth that was reported by At-Tabaraani in Al-Awsat on the authority of Anas 
  who said: “When the Prophet 
  used to look in the mirror, he would say: “Praise be to Allaah Who fashioned my creation and gave it a perfect form and Who shaped my face in a good form, and made me among the Muslims.” However, this Hadeeth is Dha’eef [weak]. 
Allaah Knows best.