I dont like them. For two reasons:
1) put "-ambient_factor 75" to your command line - With that much ambient lighting theres no real feel to those images
2) dont use the old old old thruster graphics there - They're what seems to be the first version of them ever made (the little bad quality jpgs). Use either the ones from my 32bit zip, Bobboau's versions, or the latest effects: The Hybrids. Download and stuff can be found on my website (first link in my sig).
Else than that: nice to see someone making use of my backgrounds

You should blur the alpha of the planet atmosphere a bit more, it looks a bit cut off for an atmosphere - really nice planet though. Oh, and there's a square box visible around the sun. Make sure all the sun images are faded to $RGB 0,0,0.