I just inspected it to see how they did the animations for those. Something in javascript is updating the img src attribute at 60fps, which is an absolutely insane way to code that IMO
Right, surely the icons could be SVGs, with the background orbs stored as a base64 PNG (or maybe a specular lighting filter?), with the foreground icons made to move via an updating displacement map?
Even if they didn't want to go that route, What I've seen google do in the past is render every frame to a texture atlas, and write a CSS animation which updates the background-position property at 60 frames a second, so at least you don't have to load 150 images at a time
Everything comes back in fashion again.