Curved background image in CSS

Question

I'm trying to achieve something like in the picture below (curved background image) from state street website, but in CSS.

The issue is that my curve... is too curvy. I'd like it to be more "straight" like the state street one.

Is it possible in CSS?

body {
  margin: 0;
  background: red;
}

div#back {
  position: relative;
  height: 200px;
  background-image: url(http://wearepeak.co.uk/wp-content/uploads/2016/02/testimonial.jpg);
  width: 100%;
  border-bottom-left-radius: 70% 60px;
  border-bottom-right-radius: 30% 10px;
}