Disposing images

I have noticed that the GoImage class does not dispose the images it stores. ( no IDisposable derived class )
What would be the best method for implementing disposal of images properly, along the deletion of the objects ?
Best regards,

GoImage was designed with the assumption that the Images it displays are shared with other GoImages. Also, “deleting” a GoImage from a document just removes it from the document, but it might come right back if there’s an Undo.