You can have a larger logo.
In includes/languages/english/YOUR_TEMPLATE/header.php, look for:
Code:
define('HEADER_LOGO_WIDTH', '192px');
define('HEADER_LOGO_HEIGHT', '64px');
define('HEADER_LOGO_IMAGE', 'logo.gif');
and change it to:
Code:
define('HEADER_LOGO_WIDTH', '223px');
define('HEADER_LOGO_HEIGHT', '200px');
define('HEADER_LOGO_IMAGE', 'logo.gif');
This may throw off your page width, but you can probably adjust the logo size later.
If you look at the Holzheimer site in my sig, the logo is 176x185. The logo for the Fan Odyssey site is 862x110.