That is certainly possible but I thought making sure the picture resource you have works on another system we could at least eliminate that as a possible cause. You could just upload the .tif as long as that would not violate any copyright issues. In the mean time I will find a .tif of make one with an alpha channel and follow the published tutorial instructions and see if it works here for me and let you know.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675