Oh man!
You are gunna hate me brother!!!
I like your scene and the lighting is fab!! I have a few suggestions that might help with it.
It seems that when I look at it, it looks "small" It does not look like a planet (apart from the really good lighting) It looks more like a model planet.
Here are a few things that may help!
1, when you take a picture of landscape with a camera, there is no depth of field so the forground and the back ground are usually in equally sharp focus. Perhaps by removing the blur on the moon and the star field, you will increase the feeling of depth.
2, I think that your bump and texture maps are too "chunky". I had the same problem when I was texturing the road that the car drives down in the vid on my site. Someone pulled me up and said the car looked like a model. I reduced the size of the dirt and textures (what a pain) by over 75% and it looked better.
I have been very presumptious and I have roughly tried to alter your image (in Photoshop) to give you an idea of what I mean. I hope you're not offended.
This is only my opinion.
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