Try restarting Steam and check if any updates are available for your games. If the icons aren’t restored, try deleting the appcache folder in your Steam directory and restart the client. The icons should re-download. If that doesn't work, reinstall Steam without removing the game folder this should restore the icons.

https://psteamcommunity.yuanyoumao.com/discussions/forum/1/4031348273658006638/#c4031348273663363784