crispex@
the cloud renderer is a really bad thing to use, I'd almost say that you shouldn't use any filters other than one or two of the blur ones and only if the effect can't be achieved with the blur tool
What you really need to do is work on your colour correction skills (you'll find this setting under
image > adjustments > color balance), if you're trying to combine two photos this is the key stage as it is at this stage that you're trying to match the envirmoental lighting from your background to that of your subject. However this is still not going to be enough, after this you need to make sure that the lighting for each thing matches, for nistance in your second image the Ti fighter has very different directional lighting to that of the background.
Once you have done this you have to match perspectives, ensure that if neccessary the light from the subject affects that of the background etc
And as PW Productions said, make sure that you make their contrast levels match on top of their colours.
Your first image does this to a greater degree, although there are still some issues to tackle.
