I have images of equal aspect ratios (300px x 255px) in divs taking up ~31% of the width to make 3 columns on desktop/tablet, then full width on mobile. The images scale to
You could try using view widths to keep the proportions on resize:
HTML
Here's a title
Here's a title
Here's a title
CSS
.hotels {
display: inline-block;
width: 31.8vw;
height: 26.3vw;
vertical-align: top;
margin-bottom: 22px;
background-image:url(http://www.telodesign.com/test/cavallo-300.jpg);
background-size: cover;
}