They bear a striking similarity to Fayum (or Faiyum) funerary portraits from the first and second centuries A.D. in Egypt. Yes, EGYPT, I know, they don't look "Egyptian". But at this time in Egypt's history, they would have seen rule by both Greek and Roman forces so the portraits become an amalgamation of a Greek style of painting with Egyptian funerary practice of mummification like you can see here on the website of the Metropolitan Museum.
All of the figures look familiar in some way but the woman all the way to the left in this top image is very close to this portrait in the British Museum currently. You can find a lot of similar works and some that must have been the inspiration for these paintings on Wikimedia Commons here and I found the man with the seven-point star headdress in the bottom photograph as being identified as a priest in this Smithsonian Magazine article from 2012.
Gardner's page 288