Just seconding the idea of vineyards. A berry bush is a poor substitute. Vineyards have a visible trellis and you should be able to place them in ranks. It could be a scenery object, or a gatherable resource a civ could build in-game. Another fan of fruit trees. It doesn't have to be spectacular. Just add some golden yellow (apples, citrus, figs) or reddish purple (plums, cherries, black figs, olives) flecks to an existing tree with a roundish, even crown. Take a palm tree, add some reddish brown clumps at the top, you have dates and oil palms. Again, it could be a Gaia harvestable object, similar to berry bush. Or it could be part of a buildable cultivation area, an orchard, specific to a certain civ or multiple civs. Lastly, be aware that by 0 AD, Greeks, Romans, and Persians all had contact with subsaharan Africa, east Asia, and the subarctic. You may wish to leave open the possibility for a roleplaying campaign in one of these frontier areas. Adding in a small number of selected exotic flora, fauna, and relics from these faraway markets will add to the potential of this game. Alexander's men were acquainted with tigers from southeast Asia and India, there was a Greek market town on the Strait of Malacca, and captive Greek and Roman artisans were often taken abroad by Scythian and Parthian warlords to work gold on the frozen steppes and mountains in central Asia. For this reason, there's also a case for making a small subset of snow terrains that correspond with European and Asian terrain types.