While the Bible was still being written, it was not unheard of to actually see God. John saw him as he wrote “The Revelation”, Paul saw Him on the road to Damascus, he lived 33 years on the Earth in front of men, and he appeared at different times to different people in the Old Testament.
We get a little bit of an idea of what He looked like in human form from Isaiah 53, which tells us that Jesus was not an attractive man—”there was no beauty that we should desire Him.”
So why not appear on Earth when there were good painters or photography so that we actually knew what He looked like?
The Point of the Message
The point of the Gospel was never to attract people to an image—Jesus appeared as a person, but He is the Creator—a spirit. He is more glorified than the image He had when He was here.
And I think that was part of the point then. He arrived, not as a king in Earthly means, but as a baby to a humble family. He was not physically appealing—like Saul or David, but He could have been whatever He wanted.
The point was the message, the death of King for the sins of the World.