Here are few tips how to change the images, so it will have different images for different languages
If they are added using CSS, change line 39 of header.tpl in your theme's directory from :
<body {if $page_name}id="{$page_name|escape:'htmlall':'UTF-8'}"{/if}>to something like
<body {if $page_name}id="{$page_name|escape:'htmlall':'UTF-8'}"{/if} class="lang{$cookie->id_lang}">So that you can target any object of the page for a specific language. For example, the following code gives the website's a different background depending on the current language :
body.lang1 { background: url('../img/bg_en.jpg'); }
body.lang2 { background: url('../img/bg_fr.jpg'); }