It is possible to parse dynamic values in a couple of way.
Interpolation with double-curly braces:
ng-style="{'background-image':'url({{myBackgroundUrl}})'}"
String concatenation:
ng-style="{'background-image': 'url(' + myBackgroundUrl + ')'}"
ES6 template literals:
ng-style="{'background-image': `url(${myBackgroundUrl})`}"