Если вам не нужны "хлебные крошки" и меню выбора языка/валюты, то в файле catalog/view/theme/default/template/common/header.tpl находим
<div class="div6">
<div class="left"></div>
<div class="right"></div>
<div class="center">
<div id="breadcrumb">
<a href="http://demo.opencart.com/index.php?route=common/home">Home</a>'>http://demo.opencart.com/index.php?route=common/home">Home</a>
> <a href="http://demo.opencart.com/index.php?route=checkout/cart">Basket</a>'>http://demo.opencart.com/index.php?route=checkout/cart">Basket</a>
</div>
<div class="div7">
<form id="currency_form" enctype="multipart/form-data" method="post" action="http://demo.opencart.com/index.php?route=common/home">
<div class="switcher">
<div class="selected"><a>Pound Sterling</a></div>
<div class="option">
<a onclick="$('input[name=\'currency_code\']').attr('value', 'EUR'); $('#currency_form').submit();">Euro</a>
<a onclick="$('input[name=\'currency_code\']').attr('value', 'GBP'); $('#currency_form').submit();">Pound Sterling</a>
<a onclick="$('input[name=\'currency_code\']').attr('value', 'USD'); $('#currency_form').submit();">US Dollar</a>
</div>
</div>
<div style="display: inline;">
<input type="hidden" value="" name="currency_code">
<input type="hidden" value="http://demo.opencart.com/index.php?route=checkout/cart" name="redirect">
</div>
</form>
<form id="language_form" enctype="multipart/form-data" method="post" action="http://demo.opencart.com/index.php?route=common/home">
<div class="switcher">
<div class="selected"><a><img alt="English" src="image/flags/gb.png"> English</a></div>
<div class="option">
<a onclick="$('input[name=\'language_code\']').attr('value', 'en'); $('#language_form').submit();"><img alt="English" src="image/flags/gb.png"> English</a>
</div>
</div>
<div>
<input type="hidden" value="" name="language_code">
<input type="hidden" value="http://demo.opencart.com/index.php?route=checkout/cart" name="redirect">
</div>
</form>
</div>
</div>
</div>
заменяем на
<div class="div6">
<div class="left"></div>
<div class="right"></div>
<div class="center">
<div style="text-align:center">текст</div>
</div>
</div>
или (в случае картинки) на
<div class="div6">
<div class="left"></div>
<div class="right"></div>
<div class="center">
<div style="text-align:center">
<img src="путь к картинке" alt="" />
</div>
</div>
</div>