It is narrated from Sayyiduna Anas bin Malik, may Allah be pleased with him, that the Noble Prophet, peace and blessings be upon him, said: "The Hour will not be established until people boast about their mosques."
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1446
The meaning of the hadith is that near the Day of Judgment, people will boast to one another, saying, "My mosque is taller, more splendid, more adorned, and more decorated."
From this hadith, it is understood that decorating and illuminating mosques beyond necessity is prohibited.
The real adornment of a mosque is to keep the mosques populated, to perform prayers in them, to recite (the Qur'an), and to arrange lessons and teachings, etc.