Thanks guys.
T-rex - in the end, I cut a sheet of cork into brick like shapes. Some I broke more than others.
The white pieces you see are acutually kitty litter. I only removed the larges pieces. I also added some broke pieces of Balsa wood and match sticks. I have to use a heavy, dark grey wash to color the rubble. The cork actually absorbs most of the color. I then picked out a couple of bricks with slightly lighter shades of grey.
As for the Firefly appearing a blueish, that's probably down to my photography skills (or lack of). It really is actually OD, I promise. Could have been effected by the light at the time. I've submitted a post to this forum with the completed work :
( /forums/760606/ShowPost.aspx ).
It looks a little better in those shots. Also, the uniform colors of the US patrol are incorrect for that uniform style. I just took creative liecence with them, so they aren't historically correct.
Detailfreak - the doorway might look out of scale due to the angle of the photos. With a figure standing in the doorway, the top of the doorway is just above his head.
cheers guys and many thanks again for the comments.
Jurgen.