This shot is of a Romeo and Juliet sculpture in Central Park near the Delecorte Theatre. The theatre shows free Shakespeare plays in the summer. I thought looked particularly nice in black and white.
The vignetting effect on this shot was done using the Post-Crop vignetting panel in lightroom. There are actually two areas that control vignetting in lightroom. The first is under Lens Corrections. This area is more designed to correct for natural vignetting that occurs from lens imperfections. This type of imperfection will of course only show on the corners of your shot, and will disappear if you crop off the corners. Therefore, if you crop your shot, these lens correction vignetting adjustments will not “travel” with your crop.
Because people started using vignetting as an artistic effect, Adobe added the Post-Crop Vignetting panel under Effects. Like the name says, the vignetting here will be maintained on any crop of your photo. There are various styles of vignetting that you can do here and you can experiment with them yourself.
Now you know, and knowing is half the battle.