Changing The Background Image On Collection List

Store Design
1

I’m attempting to do exactly what the post below solves, however, there solution isnt working for me. I’m using the dawn theme opposed to the ride theme, url: http://opaliquebeauty.com/

Post: https://community.shopify.com/c/shopify-discussions/changing-the-background-image-on-collection-list/m-p/2421417

Any help would be much appreciated