Install mate-icon-theme-faenza by entering the following commands in the terminal:
sudo apt update sudo apt install mate-icon-theme-faenza
Description:
MATE Faenza Desktop icon theme
This package contains the Faenza icon theme provided with the MATE desktop. . The icons are used in the panel menu, and in caja and other applications, to represent the different applications, files, directories, and devices. . This theme has been made by Rowen_Stipe based on Faenza and Faience icon themes by ~Tiheum.
Homepage: http://www.mate-desktop.org/
Version: 1.20.0+dfsg1-0ubuntu1
Section: universe/x11