There does not seem to be a way to use a custom sized icon in the menu of XFCE. This is what I cobled together from different online resources:
- Install and enable whisker menu
- Create a transparent image (see comment for a example file)
- Choose this transparent image as the icon for whisker menu and select to show icon only
- create a gtk.css under ~/.config/gtk-3.0/ with the following contents (change size as wanted):
#whiskermenu-button {
background: @launcher_bg url("/path/to/icon") center;
background-repeat: no-repeat;
background-size: 64px 64px;
margin-top: -2px;
padding-bottom: 0px;
}
- Finally logout and login again to apply the css setting.
transparent.png