I would say do not use flags unless you don't mind being dragged into world politics :-) I can give you the example of Arabic that is the national language acr

I would say do not use flags unless you don't mind being dragged into world politics :-) I can give you the example of Arabic that is the national language across 22 countries. Which flag would you choose there? The thing is flags come loaded with nationalistic sentiment. You will be dragging yourself into the middle of many political conflicts worldwide. Taiwan/China is one but you will also have Israel/Palestine, Kosovo/Albania and likely others. Users from one national tendency will quickly point out how their flag should be there. Of course if you are only supporting a few languages this may not be a big issue.