A nameplate would be eligible to submit as representing an eligible location. For example, a nameplate for a park. I am not sure what you are calling a “nameplate” so it would help if you could provide photo examples.
We don’t know why some submissions are rejected by the automatic checker ( nickname Emily). They can be very frustrating. But you can appeal those rejections.
There is no “should accept” that applies to a submission.
Each submission should be assessed on its on merits, what it is, its function and if the submitter has made a reasonable case that it is good enough.
A good way to convey that somewhere is a social space might be to have as a supplementary photo a picture that shows it in use - try to take from a distance so the people are not close up and the people should not look posed or be looking at you directly as otherwise it could be considered as an attempt to influence reviewers.