Is there a way to not fetch images in data source descriptions

Is there any way to tell Cesium to not prefetch the images in the data source descriptions?

We have 1-2 image URLs in a KML Data source description. Cesium fetches all the images on load. Google Earth only prefetches them when you click on them. Is there any way to do this is Cesium?

I looked at the KML Data source API and do not see any way to do this off hand.