Chariots on Mycenean steles, 16th C BC, now in the National Archaeological Museum in Athens:
Egyptian hunting from a chariot, facsimile of a fresco from the tomb of Userhat, 15th C BC:
Tutankhamun single-handedly smashing the enemy army, from his tomb, 14th C BC:
Ramesses II on a chariot on relief from Abu Simbel, 13th C BC:
Two-horse, three-man Hittite war chariots, drawn from Egyptian reliefs:
Chariot model, Early Iron Age, Eastern Geogia:
Assyrian king hunting lions, relief from Nineveh, 7th C BC:
Assyrian two-horse, four-man war chariot on a relief from Nineveh, 7th C BC:
The Etruscan Monteleone chariot, c. 530 BC, which survived intact, and is now in the Metropolitan Museum in New York (I'd love to see this in game, perhaps for a Roman hero?):
Four-horse chariots depicted on the Greek Vix krater, c. 510 BC:
Darius on a chariot hunting lions, Assyrian-style, seal impression:
Libyan with biga depicted on the Apadana of Persepolis (c. 500 BC):
Persian biga, also from Persepolis (c. 500 BC):
The only two-beam and four-horse yoke example I know of, the Achaemenid gold model of a (ceremonial?) chariot from the Oxus treasure, now in the British Museum:
Four-horse chariots from the Terracotta Army (246–208 BC), China:
Ashoka on a two-horse chariot, as depicted on the southern gateway of the Sanchi stupa in India, c. 1 BC:
(All these photographs are from Wikimedia Commons.)
I'm hoping @Genava55 and will provide some quality images of Celtic chariots, and @Sundiata for the Kushites. Depictions of Carthaginian war chariots (attested in Greek texts) would be more than welcome too!