When a movie is rated R (R certification), tMM shows a R image on the upper right portion of the main view. Same for PG, PG-13, etc. When the movie is NR, there is nothing there. Is it possible to add a NR image in such cases?
To start, there is a typo in the subject, could you fix that? NR should be defined as "Not Rated". My mind must have been somewhere else when I typed that.
With that correction, there would be no listing for a rating of NR (not rated) because it is not rated. This is seen a lot on movies as "Unrated". Taken from the link / URL you provided:
"An unrated film is often denoted by "NR", such as in newspapers, although this is not a formal MPAA rating."
we've taken the official logos for the certifications to display it in the UI.. if there is no NR (and thus no logo), we have to create a own one...
I've found an adequate images and will be included in the next version