In addition, those are POST ICONS. And they can easily be added/removed.
Control Panel > Images & Icons > Post Icons
Image Sprites are a collection of images put into a single image.https://css-tricks.com/css-sprites/
This is not appropriate usage for easy customization of Post Icons, Graemlins, Avatars, Forum Images, News Images, and Moods, where a forum owner would want to replace one or two images with their own custom image/images to fit their forum presentation. Especially if a single page was displaying 5 of sprites from a package of 100. All of those colorful 100 sprites would need to be downloaded when just 5 of them were needed.
CSS Sprites animation -https://itnext.io/creating-css-animations-using-sprite-sheet-47e2b7a3793c
Now dump your 50 gifs in to that and have all of their animations in that single file.
Does this even make sense to do