Another widely mentioned suggestion is to beware of implicit cultural assumptions when designing interfaces for multiple cultures. Most of the time the example given is the ‘American mailbox’. I did not succeed to find any modern interface example with such a metaphor.
However, I spotted one icon which is loaded with assumed cultural knowledge — the ribbon on the finger, indicating ‘remembering something’. It is used, for example, in Inbox by Google. Although it is a very nice metaphor on its own, it is not widely understood in other cultures