Standard Memorial Benches are not eligible…
https://community.wayfarer.nianticlabs.com/t/seating-benches
The only chance is the “Bench with a view” option.
I am not a big fan of these as all benches have a view so different reviewers will have different opinions of which views are “good enough” to be accepted.
In these cases you are nominating the view and not the bench in the same way as a Trail Marker is nominating the Trail and not the Marker.
Good Luck.