Rasul (ﷺ) used to say when watching himself in the mirror:
اَللَّهُمَّ حَسَّنْتَ خَلْقِي فَأَحْسِنْ خُلُقِي
Pronunciation
Allaahumma hassanta khalqi fa a'hsin khuluqi
Meaning
O Allah, just as You have made my external features beautiful, make my character beautiful as well.
Source: Sahih (Albani). Musnad Ahmad: 5099
Duas from IslamicAPI's Masnun Dua dataset (based on the Quran, hadith, Hisnul Muslim and Rahe Belayat). See the dataset