In T246792 @Gilles had a good suggestion for improving the lazy-loading images in search results:
While the image lazy loading is a great idea, it seems like it's not doing enough "look ahead", images only start loading when they get into the viewport. By using an Intersection Observer with a properly set rootMargin parameter, you can actually have images that are slightly below the viewport get loaded. This would ensure a lot smoother scrolling experience for users with reasonably fast internet connections, who would never see a loading thumbnail.
This should be pretty straightforward to fix.