Recently I found a few pages of objects with images no very cropped. At first glance they would not be detected because the background is white.
For example, by selecting all the text you can see the uncropped background here https://en.numista.com/catalogue/index.php?e=canada&r=&st=150-149&cat=y&im1=&im2=&ru=&ie=&ca=3&no=&v=&a=&dg=&i=&b=&m=&f=4&t=&t2=&w=&mt=&u=&g=&se=&c=&wi=&sw=
My suggestion is to show a border in a color that stands out in images of modification requests. This way, the referee and the contributor can see if an image could be cropped further.
For example,
