Today I added the ability to select custom icons for languages in the Editor.

How to Select a Custom Icon?

To select a custom icon just follow the next steps:

Click the popup menu in the toolbar.
Click the Options button of a language.
Click the Select Custom Icon option. The object picker prompts you to select a Texture2D.

NOTE: The size used by built-in flag icons is 16x11 pixels. But you can use textures with any size.

How to Remove a Custom Icon?

To remove a custom icon just click the button with a cross drawn at the right of the Select Custom Icon option. See the above image.

NOTE: This button is drawn only if the language has a custom icon.

The custom icons are displayed in the popup menu of the CGLocalization window toolbar and in the Languages window:

Also in the HierarchyView in gameobjects that has the ChangeLanguage script attached:

NOTE: This update will be available in the version 1.2 of the tool.