Pretty nice for sure. I like how you have multiple planets and a few close stars. I like how the planets overlap too. The widescreen format is a plus.
Things I would improve would be the texture on the largest planet (seems a bit flat and soft), and the overall image sharpening (drop this down some), as it enhances the color gradient banding. Even better would be to use Photoshop to selectively add sharpening where needed.
Additionally, the terrain is a bit 'too' perfect and aggressive. Maybe you can run it through another erosion filter in World Machine (like a flood of slurry)? That oughtta tame that terrain!
