I would probably prefer to use text other than "Please wait..." since it won't work if JavaScripts are disabled. This can be fixed by changing the text to something such as "This is a HTML/ZIP/PNG polyglot file". And then, omit the <title> to save space.

The URL jar:https://raw.githubusercontent.com/gildas-lormeau/Polyglot-HT... can be used to display the HTML file in some web browsers, although it cannot display the PNG file in this way since it uses # as the URL of the picture.