Do not use a country flag to represent a language - there are countries with multiple languages that are not spoken in other countries. Example: South Africa has 11 official languages, of which English is the only one spoken internationally.
Why not use flags for languages?
countries or nations. Languages represent a shared method of communication between people. Flags are unique to a country or nation: but languages are often spoken across national borders. By using a flag for a language, you may confuse or even offend users.
Do languages have flags?
Flags representing languages? While many languages naturally can be indicated by one or another national flag or in some cases a regional flag, for some other languages no such flag is readily at hand.
How do you visually represent a language?
There is no natural graphical representation for a language. The only acceptable icon for a language is its two letter code as it is used in the Windows standard language toolbar. Even with this icon, it is highly recommended to put the language name in plain text, preferably in its native form.