And make sure you have lots of slight variations to avoid monotony. Good composition is also important. Real scenes have fog, mist, depth of field. A color scheme adds to the atmosphere. Further away objects have cooler, less bright colors.
Closer objects are brighter and livelier.
Even in a still image, a sense of movement is important. I find the best way to do this is to add lots of details, either with geometry or textures. Use lots of them. Even similar objets will never have exactly the same sort of texture. Play with shininess maps.