I'll add a bit to the great advice already given with one disclaimer - I'm not a great artist, or even a good artist, just someone who enjoys working with 3D. I'm still learning, and what I consider good another person might think is really bad. Personal preferences are very important to determining what an individual thinks is a great render or a not so great render.

From the image above, and looking through your gallery, like others have already said, lighting is one of the keys. But, materials and shaders are equally important, and typically will need to be adjusted to the lighting. There is a very close interdependence between the two. It is a rare occasion when I use any materials/shaders exactly as the came from the vendor.

For a quick example, in the image you posted above, the clothes definitely need some shader work to make them match how the lights are affecting the skin on your model. The dress looks flat in comparison to the model and the wings. I would begin by adjusting the specular settings to improve the interplay of highlight and shadows on the dress.

I would also reduce the brightness of the background image a bit. It is almost creating a silhouette effect making it hard too focus on and see the figure due to the brightness of the sky (but this may be the effect you wanted).

Take a quick look at my gallery (link in my sig line below) to decide for yourself how much weight to place on my comments. My comments reflect what I would do when preparing a scene to render to fit what I like to create. My style may not really be what you are after. It typically takes me 5-20 hours (often more) to compose a scene, I'm a test render alcoholic, continually adjusting materials or tweaking lighting, then test render, and repeat this process over and over until I get things to where I feel it's the best I can do with the image. As I gain more experience, the speed of this process improves, but I'm still learning.

Hope this helps.

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