By carefully walking around and sighting up through the pipes, you can see the four evangelists have been roughly painted. There is still much detail to be added.
Perhaps more interesting are the four beasts which also represent those evangelists. The tradition of using animal figures is an ancient one. Read more about them here. This icon was done by British iconographer Aidan Hart, and has the four beasts surrounding Christ, representing the spread of the gospel to the four corners of the universe.
And here's a fabulous icon, where in each corner you can see one of the evangelists, seated at a desk and accompanied by his representative beast.
The four beasts (as a group) may also be referred to using the term Tetramorph, meaning four shapes. Read more about that here.
The ox
The eagle
The man
The lion
As we look at the ceiling we can catch glimpses of Christ looking at us.
If you could climb up into the drum, you could see the Old Testament prophets appear in completed form. These were painted on canvas and then affixed to the walls with special adhesive.
The largest one is Elijah. He is positioned directly across from Christ.
This final painting is not yet completed, but you can see it in the bright light cast through the dome's windows.
While high above all the other details and images, the Pantocrator on the dome raises His hand in blessing.