Here's how:
- Create a new language string in Admin CP > Languages > Manage Phrases, called logofilename. Assign it the name of your logo for that language, for example: mylogo-en-us. Follow in the same way for your other language, for example: mylogo-en-uk.
- Add the relevant .gif graphics to /themes/client_default/
- Edit the header template in Admin CP > Templates > Manage Templates > General.
- Locate the following tag set: <img src="<{$themepath}><{$product}>.gif" border="0">
- Change it to: <img src="<{$language[logofilename]}><{$themepath}>.gif" border="0">
- Save the template.
- Make the same change for other template groups, as needed.
You can apply the same principle to other graphic images.