Image with arched edges
Arched edges is to introduce the pseudo elements :before and :after, size them relative to the container, and transform: rotate(-10deg);. Setting a hardcoded left and right ensures that the pseudo elements lie on top of where the image's shadow lies.
Rounded drop shadow
Here is another CSS technique for creating border shadows and dividers by utilizing curved CSS box shadows, the :before and :after pseudo-elements, and border radius.