One consideration for the game is the role of current day religions, some of which would exist in this time period. (Judaism, Hinduism, Buddhism, Jainism, Zoroastrianism, Confucianism, Shinto, and Taoism come to mind.) In Green Ronin's Testament game, the differing faiths of the ancient Middle East are treated as part of a whole. Thus, one character could play a priest of Ra and another a prophet during the reign of King Solomon. I have Testament, and I would recommend this approach.
As for non-human races, possibly some could enter or reenter the world when magic starts. (Or is it restart.)
There also was a good thread on the Wizards board on an industrial revolution. One thought about why the ancient world did not have an industrial revolution, despite the presence of some steam powered devices and other tools, is an attitude towards technology. This view holds that the Greco-Roman world's view as labor being beneath an educated man tended to discourage practical application of science. Another thought is that the presence of cheap labor, namely slaves, also tended to prevent people from working on labor saving devices. If there had been a major war some decades prior to the start of the game, population levels and workforce levels could be lower -- thus prompting more of a desire for labor saving devices.
Kalanyr, history is a hobby of mine, so I can help with research if you need it.