edit core/local.config.php
# Options for the signature that's generated
Config::Set('SIGNATURE_USE_CUSTOM_FONT', true);
Config::Set('SIGNATURE_FONT_PATH', SITE_ROOT.'/lib/fonts/tahoma.ttf');
Config::Set('SIGNATURE_FONT_SIZE', '10');
Config::Set('SIGNATURE_TEXT_COLOR', '#eeeeee');
Config::Set('SIGNATURE_SHOW_EARNINGS', true);
Config::Set('SIGNATURE_SHOW_RANK_IMAGE', false);
Config::Set('SIGNATURE_SHOW_COPYRIGHT', false);