Lumion is driven by a powerful game engine but that doesn’t mean your renders should look gamey! There are plenty of ways to create subtle realism, atmosphere and aesthetically attractive images.
Check out this tutorial from Chris Welton, who is well-known to the Lumion team for his skills and knowledge of Lumion. Among other things he explains about getting the lighting right, setting up the materials and using the Lumion effects to get the best results. Definitely worth a watch!