I tried viewing John Derry's amazing "Impasto Varnish" on his blog, but the photos all appear as a white square with red X. Can someone influence John to fix that problem so we can all enjoy his "Varnish" tool?
Do you mean the photos in his Interpreted photograph step-by-step post?
If so, the link to the John's Impasto Varnish images zip download is also broken in that post, but can be downloaded here.
John's finished Bamberg image can be viewed in this thread at the digitalpaintingforum.com website (membership required).
Additional images (possibly not included in the original Painter Factory blog post, but presumabably using the same varnish image resource can be seen in this thread at the fredmiranda.com forum.
Sorry I can't help with the original image links.