FIGHT ON, I don't know anything about a MAC. I don't know very much about ANY computer. The only way I know how to make a desktop pic, is to right click on it, then pick "save as background". Which I did, for your beautiful pic.
Well, you know a whole lot more about photography than I do. I have a Canon A-520 Powershot, the memory chip is full (250 pics or something), and I don't even know how to put them on the computer, to clear the chip, so, basically, the camera is useless. I think I'm hopeless in this regard.