We have made changing the background extremely easy with the front end live designer. When you're in live design the default view is preview. You will need to click on the design icon shown below.
Change the view to Backgrounds by selecting it from the drop-down box at the top.
If you want to use a solid color, simply type in the hex code for the color or select the color and a color wheel will appear as shown below.
If you want to use a background image, you can select the folder with the arrow shown below.
