hmm
alrite.....
u have some of the basics down....
but now, just take them further....
for instance.....u see the lighting on the stock/render of the astronaut???.....
it makes the light source seem much larger than the light source u placed there.....
ie. make the surroundings of a sig FIT the focal stock/render....
the colour of the lighting on the render is orangey yellowey type thing.....
have a go at adjusting the colour and size of the lightsource so it seems more realistic to the render =]