Images of the enthroned St. Peter were not unfamiliar in this period. Here is one by Giotto from 1320 (also from the Pinacoteca Vaticana):
View the di Ciono panel and the Giotto altarpiece in full resolution.
Read more about St. Peter.
Jacopo di Cione, St. Peter
1370-71
Tempera and gold on wood panel
Pinacoteca Vaticana, Rome
The festive scene with bugles may suggest the Feast of St. Peter's chair on February 22. With his pointy beard and bald forehead, the one haloed figure on the left should be St. Paul. The two kneeling figures may be the donors. The others seem not to be saints. They do not have haloes, and one of them wears the conical Jewish hat. Perhaps they represent the citizenry as a whole.
Images of the enthroned St. Peter were not unfamiliar in this period. Here is one by Giotto from 1320 (also from the Pinacoteca Vaticana):
View the di Ciono panel and the Giotto altarpiece in full resolution.
Read more about St. Peter.
Photographed at the Pinacoteca Vaticana by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.