Let's not localize filenames, please.  Users aren't supposed to have to know about files, so the name will rarely be visible. Also, if you use the same "unnamed" name each time, the algorithm for finding a suitable version number will slow to a crawl.

Instead, I suggest actually using lastIndexOf('/') to find the entire filename of the cropped file, not just its extension.  That way you get something that already has a unique name.