The GNOME desktop provides several themes that are designed for users with special visual needs. For example, some of the themes are designed for users with low vision. The themes contain several versions of each icon so that the icon can be displayed in each theme.
You might need to install a new icon for an application. When you install a new icon, you must create several versions of the icon, so that the icon displays correctly in the themes. You can create the icons in several formats, for example Portable Network Graphic (PNG) format. The suggested size of icons for the GNOME desktop is 48 pixels by 48 pixels. At this size, most themes can rescale the icons.
When you install a new icon, create the following 48 Ч 48 pixel versions of the icon:
Low contrast icon
High contrast icon
Inverse high contrast icon
If possible, create 16 Ч 16 pixel versions of the each of the icons above also, for themes that do not require large print.
Install the icons to the image files location that is specified for the theme in To Install a Desktop Theme or To Install a Window Frame Theme. For example, to add icons to the HighContrast theme, add the icons to the /usr/share/themes/HighContrast/pixmaps directory. Add references to the icons to the relevant theme files. For example, to add icons to the HighContrast theme, add references to the icons to the /usr/share/themes/HighContrast/gtk-2.0/gtkrc file.
The instructions above apply only to the following types of icon:
Icons that are used within applications in the GNOME desktop.
Icons that are used internally by GTK+ applications, or GTK+ stock icons.
For more information on how to create icons for application launchers and for panels, see http://www.freedesktop.org/standards/icon-theme-spec.html.