Re: background image on my desktop...
Hi Straight Shooter,
Where is the original image? In fact you don't need to place the image in a particular folder to set it as the Desktop Image.
Simply right-click on the image file in the Finder and choose "Set as Desktop Image" from the drop down menu.
System Preferences > Desktop and Screensavers
and click on the "+" button to add a folder of your choice to quickly switch between images for your desktop background.
Or if you wish you can access any photo you've imported into iPhoto directly from here too.