Hi Peter,
You don't need the ZIP file, you can just install the theme directly from the Moodle plugins DB: https://docs.moodle.org/32/en/Installing_plugins#Installing_directly_from_the_Moodle_plugins_directory
And if you could list the exact steps you did to cause the problem, as I looked earlier and saw nothing immediate in the theme where I'd put the URL or understood how you uploaded the image to the server, then we could determine if its a theme issue or something else, especially as you're now getting the same problem with the Clean theme, which is not beta.
Kind regards,
Gareth