The pink cloud next to the blue towers looks odd with the vertical shaping, and competes with the towers and the moons for visual dominance.
The snowy mountain is a bit too high contrast compared to the rest of the image, while the black space ships are too dark, looking like painted spots with no depth.
The blue towers show odd blue shapes (reflections of each other?) that are inconsistent with their placement, and distracting, particularly the one on the front of the rightmost tower.
The light reflection at the bottom of the dark dome shape is misplaced, since the large clouds show a light source much higher in the sky.
And what is the white mark on the right of the rock in front? It looks out of place.

It's a really good composition, and has good visual flow, you just need to adjust your lighting, reflections, and that big cloud.

MossyB, I am so glad you like it. As for the reflections and refraction's on those towers...I suppose you are a bigger expert on how the software handles light than the folks that created the software. There is only one light source and it was set by the program a single sun. I am very happy you noticed the clouds I wanted them to be stark looking and a dominant force in my scene. The white spot on the rock...well I suppose some wildlife on the alien world has visited.

Software is not invincible, and often does not take into account the difference between a spotlight aimed at a subject, and a sun, millions of miles away, providing "global" illumination on a planet with an atmosphere...

I wonder if there's an alien version of Pepto Bismol for those embarassing travel moments?

Why that spot of nature adds a good deal of realism to my picture, thanks for spotting that I had not even noticed until you pointed it out. Funny what draws certain peeps eyes, no wonder you said my picture has good composition and visual flow.
Thanks!

Nice 3D work, author, this has a 50s-60s scifi look, which I love! Cool texture on the foreground elements, too.