The canonical example is hand gestures and their use in UI elements such as mouse cursors.
More broadly speaking, exposure to different languages can often make you aware of issues that are not familiar to someone who only knows English, such as e.g.: existence of grammatical gender; pluralization that has to deal with more cases than just one/many (e.g. different forms for 2/3/...); the fact that placeholders in a format string may need to be reordered in different locales; drastically different length of text in different languages; the fact that notions such as upper/lowercase are not universal; sequences of letters that are treated as single characters in some languages; etc. Now of course all this applies to non-native speakers as well, but for more "exotic" languages out there it's usually their native speakers who provide such experience.
More broadly speaking, exposure to different languages can often make you aware of issues that are not familiar to someone who only knows English, such as e.g.: existence of grammatical gender; pluralization that has to deal with more cases than just one/many (e.g. different forms for 2/3/...); the fact that placeholders in a format string may need to be reordered in different locales; drastically different length of text in different languages; the fact that notions such as upper/lowercase are not universal; sequences of letters that are treated as single characters in some languages; etc. Now of course all this applies to non-native speakers as well, but for more "exotic" languages out there it's usually their native speakers who provide such experience.