No... iven in teh full game it is just - free units, caravan, spy, finish current research, gold, becomes our city (sometimes even if you are not Mongols !!!), reveals map / capital / artefact.
I have a feeling, that reverd kind depends on the civilization you are playing. For example when I toold the civ that has mostly money bonuses - almost all rewards from the cities were caravans. If I take some military I reieved units almost all the time. With the technology civilization almost of of them finish my research (really funny when some barbarians forgotten in the corner of the map help you research advanced flight
)
It happens so eften, that I dont suppose it was just luck and that all reward are random.