I think of the aftermath of a battle pretty similiar to the aftermath of an unusually large concert or a festival. As in festivals there are people scavenging for empty bottles and such, local villagers must have been the next in line after the victorious soldiers had taken all the expensive and convenient stuff like weapons, shields and money. Maybe this was done just before tossing the body into the funeral pyre, so that nothing valuable would go to waste. As for casualties, I figure the guy next to you dragged you to an aid station if you got seriously wounded. I doubt there was an army that didn't have auxiliaries to take care of the injured. I also doubt there were any organized effort to take care of the enemy casualties. The fate of them were probably decided by the soldiers who found them.