It's a bit hard to explain....
But suffice to say that if it is used for all the normal activities
that a mosque does (regular mass prayer sessions, sermons, etc),
and it is generally recognised by the community that it is a
mosque, then it is a mosque. There is no prescribed architecture
that a mosque must have.
It just so happens that most of the mosques that you see with domes
and minarets follow architecture common in the Middle East.
Otherwise, anything goes... like the Hajjah Fatimah Mosque along
Beach Road, which has French and Moorish influences in its
architecture.
Likewise, it just so happens that mosques would usually have verses
of the Quran displayed on the walls. While my home does have verses
of the Quran on the walls, I don't consider as a mosque since my
home doesn't function as one.
