The Masjids are the Houses of Allah and they are the best places on earth. Allah has ordered that they be raised and honoured with the Tawhid of Allah (i.e.,monotheistic belief in Him) and his remembrance, and that prayer be established in them. In them the people learn the affairs of their religion and they are guided to what it (Islam) contains of happiness and righteousness for them in this life and the hereafter. He ordered them to be cleansed from disgraceful things, idols, acts of shirk, innovations and superstitions. He also ordered that they be cleansed from dirt, filth and impurities. He ordered that they be protected from frivolous activities, play, noise and raised voices.
Even calling out for a lost item, asking about lost articles and similar acts that make them like the public roads and business markets are not allowed. He prohibited the burial of people inside of them and building them over graves. He prohibited the hanging of pictures in them or drawing them on their walls, and other similar thing that are a means that lead to shirk, cause distractions to those worshipping Allah in them and contradicts whey they were built for. The prophet gave special attention to this as is well known in his seerah (life history) and his actions. He explained this to his ummah so that they would traverse upon his path and be guided by his guidance in respecting the Masjids and maintaining them with that which elevates them, such as establishing the symbols of Islam in them. In doing so, they (his ummah) would be following the trustworthy messenger. It is not confirmed from the Prophet that he honoured the Masjids by lighting them and placing flowers on them during the 'Eids and the special occasions. This was also not known from the rightly guided Caliphs or the guided Imams from the first generations that the messenger of Allah testified for as being the best of generations. This was the case even with the advancement of the people, and their abundance of wealth and their taking a large amount from the cultures and civilizations and availability of various kinds of beautification and colours in the first three generations. Thus, all good is in following the Prophet's guidance, the guidance of his rightly-Guided Caliphs and those who traversed upon their path from the Imams of the religion after them.
Also, in lighting lights on the Masjids and hanging electrical lamps above them or around them or above their minarets, and hanging flags, and placing flowers on them during the 'Eids and special occasions for beautification and magnification is an imitation of the disbelievers. This is imitating them in what they do at their synagogues and churches, and the Prophet forbade imitating them in their celebrations and their acts of worship.