Why not replace blocked banners with something else?
Making any change to a document could risk claims of copyright infringement. We think that merely failing to allow an included graphic to be accessed would probably not be considered an infringement: after all this is what happens when a browser is configured not to automatically load images. However, we are not lawyers, so anyone in doubt should take appropriate advice. In a context where the copyright issue is resolved satisfactorily, a proxy could simply return a status 301 or 302 and specify a replacement URL in a Location and/or URI header.
