You should select it an chose "Leave out" from Icon menu - this will create a file on the root of disk, named .backdrop that contains the relative path and name of what you left out. If you have problems having the icon left out, it is probably due to the file .backdrop not being writable somehow. And if you struggle with not being able to snapshot the icon to the location you want, you should check that the icon file (Photogenics.info) is indeed writable too - "protect Photogenics.info +rwed"