Are you talking about the main logo of your website that the theme places in? You’re just wanting a different logo to display for each language?
Are you using the WPML bridge plugin? — http://wordpress.org/extend/plugins/theme-blvd-wpml-bridge/
If so, then you have a different set of theme options for each language, and since the logo image is part of your theme options, you can set a different one for each language.