background colour definitely affects scan quality, the inside of my scanner lid is white, scanning toned copper/bronze results in very dark low contrast images - the scanner averages the dark coin/light backgound. Much better results if i put a dark blue behind the coin. For bronze with lustre, i use a yellowish brown background. Also important to crop the actual scan window as close as possible (in the preview mode) , to eliminate as much background as possible before the final scan worth experimenting, but always scan at a high res, you can always reduce the picture size later