Since we're on the subject I just made the following images...
Klingon ships with no tampering
Basically the first image is how it came out of Lightwave, with 3 lights, 3 models and a background image of the Earth. All it's had done is the standard practice of rendering slightly larger than I needed it (1280 wide) and then resized to the correct size (1024) to give some basic anti-alias. It's a common trick worth remembering.
and this one...
Klingon ships with some tampering
This one has had the image copied into a second layer on top of the first and then that new layer was blurred in a 4.0 gaussian blur. I then set the layer to 'screen' or 'overlay' and put the opacity to 50% to stop the glow wiping out the image. You adjust to suit yourself, but as this is quite a light image the glow was overpowering. I then played with the hue/saturation settings to boost the reds on the Klingon cruisers and change the blue of the planet to a slightly more alien colouring. Final touch was some film-grain and the sized down to 1024.
It's not brilliant, but it shows that there's a fair bit of post-processing you can do to an image if you want to experiment. I like to do as much as I can in Lightwave, and just tweak in Photoshop or Gimp. This is about as much as I'd ever do to a normal image. I'm not saying it's nice, it's just for illustration purposes.
The D7 comes from the LWG3D site, by the way, I just downloaded it and thought I'd try it out.