The halo is an artist’s rendering of holiness and nothing more. Halos often symbolize “sainthood” in Catholic circles, but in Ancient Greece, they were drawn behind heroes to depict more than natural light around them.
The first halo in Christian art was in fact given to Jesus and used to represent Christ, rather than holiness. Artists would often paint or depict Christ before his baptism in the Jordan without a halo, showing that the halo is a human way of recognizing God in our midst. (After the baptism, Jesus was recognized as the Messiah).
So, halos are human inventions, not God’s.