Hi there. I am having a problem changing the logo.gif. This is what I've done:

I put my logo (logo_colors.jpg) in includes/templates/custom/images/

Then I put the following in includes/languages/english/custom/header.php
// added defines for header alt and text
define('HEADER_ALT_TEXT', 'Powered by Zen Cart :: The Art of E-Commerce');
define('HEADER_SALES_TEXT', 'TagLine Here');
define('HEADER_LOGO_WIDTH', '192px');
define('HEADER_LOGO_HEIGHT', '64px');
define('HEADER_LOGO_IMAGE', 'logo_colors.jpg');