It's easy to transfer the wallpaper of your choice onto your desktop. Click on the thumbnail of the image you like and when the full size image pops up, just right click on that image and download the jpg image file either directly to the desktop by using the "set as background" command or download to a folder that you have previously set up using the "save picture as" command.  The advantage of having a separate wallpaper folder is that you can put all your favorites in there and dip into the folder when you want a change of desktop scenery.