for the testimony of Jesus is the spirit of prophecy.
Revelation 19:10 KJV
I knelt at the feet of the angel and began to worship him. But the angel said, “Don't do that! I am a servant, just like you and everyone else who tells about Jesus. Don't worship anyone but God. Everyone who tells about Jesus does it by the power of the Spirit.” Revelation 19:10 CEV
Prophets in Bible times were mouthpieces for God. Prophets were like messengers, delivering a message to the people. They gave corrections, warnings, encouragement, instructions, and foretold future events from God.
Today, prophetic art seems to be the new buzz word for a lot of Christian art. It has become cliche, in my opinion.
You do not need obvious Christian symbols in order for art to be prophetic. If the art touches your heart and points you to Jesus, it has done it's job.