Is it allowed for someone to see his/her own body in nudity (ex. from mirror) ? I doubt this since it could be a zina of the eyes
In the Hadith, which is Narrated by Bahz bin Hakim From Sunan Ibn Majah:
from his father that his grandfather said: "I said: 'O Messenger of Allah (saw), with regard to our 'Awrah, what may we uncover of it and what must we conceal?' He said: 'Cover your Awrah, except from your wife and those whom your right hand possesses.' I said: 'O Messenger of Allah (saw), what if the people live close together?' He said: 'If you can make sure that no one sees it, then do not let anyone see it.' I said: 'O Messenger of Allah (saw), what if one of us is alone?' He said: 'Allah is more deserving that you should feel shy before Him than People.' " [Awrah is private parts]
بَهْزِ بْنِ حَكِيمٍ ، عَنْ أَبِيهِ ، عَنْ جَدِّهِ ، قَالَ : ( قُلْتُ : يَا رَسُولَ اللَّهِ ! عَوْرَاتُنَا مَا نَأْتِي مِنْهَا وَمَا نَذَرُ ؟ قَالَ : احْفَظْ عَوْرَتَكَ إِلَّا مِنْ زَوْجَتِكَ أَوْ مَا مَلَكَتْ يَمِينُكَ . قَالَ : قُلْتُ : يَا رَسُولَ اللَّهِ ! إِذَا كَانَ الْقَوْمُ بَعْضُهُمْ فِي بَعْضٍ ؟ قَالَ : إِنِ اسْتَطَعْتَ أَنْ لَا يَرَيَنَّهَا أَحَدٌ فَلَا يَرَيَنَّهَا . قَالَ : قُلْتُ : يَا رَسُولَ اللَّهِ ! إِذَا كَانَ أَحَدُنَا خَالِيًا ؟ قَالَ : اللَّهُ أَحَقُّ أَنْ يُسْتَحْيَا مِنْهُ مِنَ النَّاسِ ) رواه أبوداود (4017) وحسنه الألباني في " صحيح أبي داود ".
so, at the absolute you are allowed to do it, it is not haraam, and it is not considered ZINA, however it is proffered not to do it without any necessities as an act of being polite and shyness with ALLAH az'wajal while you are alone, and to promote the self of looking to these areas because they are place where dirt come from, and the fact that ALLAH is watching you always will enhance your faith not to sin while you are alone in general, so you accustom your self to these ideas.