If we run a bot to add a [[Category:No language templates]], we are at the same point IMHO.
A picture with an {{en}} template would be skipped. Instead we should mark it with the following categories:
[[Category: no french template]] [[Category: no german template]] [[Category: no spanish template]] [[Category: no italian template]]
etc..
This way people can work. French people work on french templates, italian on italian, and so on. If we have just a category ([[Category:No language templates]]), this will be overfilled.