This might be a solution to make fluid container height to follow it’s background image height. Same with the technique to make a fluid height video with pure CSS. Set the container height to `0` and create a large bottom (or top) padding based on it’s background image ratio to fake the container height:

Fluid Container Height Based on its Background Image Height

.fluid-bg {
background:yellow url('img/400x150.jpg') no-repeat 50% 0;
background-size:100% auto;
height:0;
padding-top:37.5%; /* `150/400 × 100` */
}