Hi,
I would like to thank everybody for their replies. I never had expected so much response for - what I think - a simple picture.
It’s great that you like the clouds but it’s only a skysphere with a texture on it. I wish I could make that kind of clouds on my own, but I have to wait until the tut from @ce rolls in 
BgDM wrote:
I actually like the clouds. The NOR could be reduced a bit IMO, but they look great. My problem is with the ground. (…) I am also not to keen on the mist/dust effect. Just doesn’t seem to fit, for me anyway.
As I stated above, there is no NOR to be reduced… 
You’re wrong with the ground. There isn’t even a plane, just lots of air. :o The slightly darker line is the horizon of the skytexture. Do you have an idea how to improve the dust-effect? It should look like flying sand.
basse wrote:
oh no, do not add any spaceships…!
imgranpaboy wrote:
dont u dare listen to basse! scifi must appear! a ship in this scene would be way too cool
I have to admit that I’m confused about this topic myself. I would like to add my spaceship (even if it’s just parking on the ground in the background) because I love SciFi. But on the other hand is this picture fine right now and I don’t know if the ship may ruin the mood. So I’ve decided to make two pictures, one with and one without that ship. And I also try the motionblur (if I manage to do it - I’ve never done this before!)
basse wrote:
I would love to see a bigger rendering though, is it possible?!
Yes that is possible. In fact, the picture I posted here is only 25% of it’s original size. I always work with big sizes to see that everything is modelled and textured well (small renderings hide errors) and to get a nice poster of it on fotopaper to enjoy it on the wall at home. What size do you have in mind? I don’t think I can post a 2500 pixels wide pic here…
X-Warrior wrote:
if some of you want the texture here it is: (i dont know for you but I always use it for making my fire/explosion…)
Thanks for the texture. I recently discovered the homepage of SysAdm
http://www.centralsource.com/blender/effects.htm
where you can find a nice rocket-smoke made with particles and alpha-textures. In the file is also a texture that is bigger than yours. Maybe you should take a look.
But if I understand @ce right isn’t that the best way to make the rocket-smoke? Please give me a hint how it could (or should) be done in your eyes 
That’s enough for now. My fingers are almost bleeding.
Greets, Tobur.