Change logo when changing languages

1. create logo for each language and save it to /img folder, with following name

logo_en.jpg
logo_ro.jpg

2. change following line in /themes/prestashop/header.tpl

<h1 id="logo"><a href="{$base_dir}" title="{$shop_name|escape:'htmlall':'UTF-8'}"><img src="{$img_ps_dir}logo.jpg" alt="{$shop_name|escape:'htmlall':'UTF-8'}">a>h1>

in

<h1 id="logo"><a href="{$base_dir}" title="{$shop_name|escape:'htmlall':'UTF-8'}"><img src="{$img_ps_dir}logo_{$lang_iso}.jpg" alt="{$shop_name|escape:'htmlall':'UTF-8'}">a>h1>