Brak's: are you using seamless paper for a backdrop? What sort of lighting set-up do you have? What camera are you using?
For this shoot I am using seamless, although, since I am usually travelling, most of my shoots are on Muslin (which I hate using after going to seamless).
My light setup is... hmmm..
I have a key light high and to the right at 45. I have a fill light a bit lower and to the left at 45. I tend to play with the intensity of each depending on the model. I have a hairlight that I sometimes use to seperate a model from the background, but rarely. I have a background light that is mounted almost directly above the model.
For a pic like the carbon freezing chamber, I had one light on the floor, under fett, with an orange gel. I had a blue gel on the background. I think I also had the hairlight on in that photo which brings in the white lining on the left side of the image.
For a pic like the vader kneeling, I had two assistants holding light down low on either side of Vader.
That is pretty much it. While 90% of my pics have the same lighting, I am not afraid to adjust and move the lights as needed for a nicer effect. The problem with that is the time and effort it takes to get those type of images... If I had more time with each person I would definitely be taking more pictures with specific and specialized lighting.
BTW, The camera I have is a Rebel XT. It is not the top of the line, but it is more camera than I currently know how to use (I am still just learning all of this stuff) and it seems to turn out photos that people are happy with.