Custom File Type Icons in Solution Explorer

Have a Visual Studio Addin that works with a particular type of (already defined) project type (not a custom project type).  Need to addcustom files for the project type.  This can be done using the EnvDTEProjectItems.AddFromFile method and works.  The new file is visible in the Solution Explorer and added to the project.

But how to display a custom icon image for the file type in the Solution Explorer?  The files have a predefined extension (e.g. filename.XXXX).

I need sample code or reference to sample code.