I am using Apex 19.2 to create different new applications and every time I would like to use a different icon. The theme default is a blu graph and in the wizard I can change the icon and the color, e.g. I can set a green folder.
In some case the correct icon is not shown and the default one in used.
From shared components -> static application files I download app-icon.css and app-icon.svg and the svg is the correct one.