Switch Language Block
This block can be added to any page (or your Page Type Defaults) to allow users to quickly switch from one language to another. Add it to an area, just like a regular block, and users will be given a basic dropdown menu listing all the available languages to select from.
Custom Templates
The Internationalization add-on includes two custom templates to help style the Switch Language block. To apply these, put the page in edit mode, click the Switch Language block and select "Custom Template" from the block edit menu:
Then select one of the two custom templates from the dropdown menu:
The Flags custom template displays a clickable flag image that switches the users' current language:
The Flags Set Default custom template displays radio-style buttons for each available language, allowing users to set a default language for the site: