L_NONE is used on several places. E.g. twice when writing a private message, once for the topic icon and also in the imageset administration.
But there may be the need to translage 'None' in different manner depending on the content. For German:
None (user) => "Kein Benutzer" or "Keiner"
None (icon/image) => "Kein Icon" or "Keines"