The types should just be translatable individually. So you'd have a language translation for "Photo" and "Photos". You should be able to find both using the language finder when using language overrides. Example as follows.
Key: PHOTO_c03d53
Text: Photo
Key: PHOTOS_5daaf2
Text: Photos
It's done this way with a substitution because there would basically be IF conditions all over the place with 100 different language strings, which can be condensed down to a small few using substitutions. There are type based language keys, but they won't work at this time due to the language key order that I'll be fixing in next release. Example as follows.
Generic Key: ARE_YOU_SURE_UNPUBLISH_TYPE
Specific Key: ARE_YOU_SURE_UNPUBLISH_PHOTO
Once I fix the language key order issue you'd use the below to specifically translate the entire string using the specific key for example on a per type basis.