Some time ago, I made a silly request to Joar, if it was possible to create an image with the four tetrarchs in the same attitude they had in the monument at the base of S.Marco church in Venice. At that point some objected, using good argouments, that the charecters rapresented in the sculpture were too stylized to be precisely identified one by one, so to speak, they were symbolic representations of the unity of the Empire.
This was not true: The Tetrarchs of the sculpture, are really identifiable and identified!
I found this news in a nice article on the Thetrarchy of an Italian researcher, A. Ambrogi, in a website devoted to Roman History.
http://www.imagoromae.com/massimiano_it.ashx
(Under the title clic on 'Articoli'/'Storia'/'L'imperatore Massimiano', free PDF download-the site and the PDF are in Italian so Google translator)
Here the images from the left: The Venetian sculpture of the 4 Tetrarchs, Diocletianus & Galerius, Massimianus & Constantius Clorus and Diocletianus.