From the Islamic point of view, we have the Qur’anic verse which speaks of the new moons. It says: “They ask you about the new moons. Say: They are signs for people to mark fixed periods of time, and for the pilgrimage.” (2: 189) It does not give any direct answer on the nature of the new moon, or why the moon is born in this particular way. It refers to the usefulness of the moon and its different stages as an indication of the passage of time. To Muslims, the crescent as a symbol of the moon remained such until the time of the Crusades when Muslims made the crescent a symbol they put on their flags to counter the cross symbol which the Crusaders placed on their flags, shields and clothes. Later, the Ottoman government made it a symbol and placed it on its flag. It was later extended to be placed on minarets. But it does not signify anything religious, and it is not associated with any religious concept. by M. C. Abdulrahman
A related issue:
A Hadith of Prophet Muhammad (pbuh) regarding signs of end time
The Mosques would be like palaces. This is clearly the case, even though the Prophet ordered simplicity in the houses of Allah, the mosques have become more and more fantastic, with golden domes, marbled floors, lavish carpets and chandeliers