So this is interesting, in order to get an SVG background image on a dynamically-generated element preload, the only way that I‘ve been able to find that works is to create literally the same element and add it to the DOM first.
Things that didn’t work:
* Making an SVG sprite sheet and adding that to the DOM
* Inlining the SVG as data
* Preloading via JS (new Image() //etc.)
* Preloading the images via link rel="preload"