So I try and make my scenes as unique as possible. Geez, I could write a book about that. First, Color . Have a unified color scheme, choose a single color or a few colors that work well together, and make sure the objects in your scene conform to this color scheme. 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.