create react app not loading css background images in dev or build

The issue was purely an issue with CSS in the App.css file:

App.css

.trees__tree {    
    background: url('../images/tree.png') no-repeat;
    background-size: 30px; /** moved this property down */
    float: left;
    height: 50px;
    width: 30px;
}

My issue was specifically that I did not have background-size: 30px; defined. Thanks for this.