Google used css sprites for Google+. They cared a lot about speed, specially for the stream, with even some CSS constructs that were known to be slow were banned from use for rendering posts.

For css sprites, you could submit an image to a folder in the monorepo, and a couple of minutes later an automated system would update the image with all the sprites, and create constants that you could you in your templates/css to use the icons with the coordinates/size of the image.