Conducting marriage in a mosque, is it a Sunnah or a voluntary act?

The important thing in marriage is publicity. One of the best forms of increasing publicity is to hold the ceremony in a mosque, where not only friends and relatives are invited, but also people frequenting the mosque may attend. The Prophet (peace and blessings be upon him) said: “Publicize marriage, hold it in mosques and beat the tambourine” [related by Ahmad and Al-Tirmidhi].
Needless to say, beating the tambourine is one way of showing pleasure. Similar methods, such as singing, are also encouraged. When the Prophet (peace and blessings be upon him) was told that the women in his household were attending a wedding, he said: “Why have they not taken with them a maid to sing?” He also suggested the wording of the song.