Because of <br /> <!-- workaround for issue 64492 - do not remove the line break! --> under token {GALLERY} I have a space on every page that shows the body background color:white.
The displayimage.php is black but it shows a white space before the footer - the br.
If I make the body background color black will show a black space before the footer on the white pages.
I made the #cpg_main_block_outer in style.css background-color:transparent; because the br is in div #cpg_main_block_outer so the br has his background-color.
I added at the end of function pageheader (copy it from themes/sample/theme.php if is not in your theme.php):
if ($CPG_PHP_SELF == 'displayimage.php') {
echo '<body style="background-color:#000000;">';
}
Depending on your theme you maybe could also remove that line. It was added because there was a minor display issue with the default theme "curve" (see here (http://forum.coppermine-gallery.net/index.php/topic,64492.msg321055.html#msg321055)).