Hi George,
do I get you right, you just want to have no picture? Then you open the file styles.php in your garden themes folder and delete all instances of leftside.jpg:
One example - before:
...
.sideblockmain {
background-image: url(<?PHP echo "$themeurl"?>/leftside.jpg);
background-repeat: repeat-y;
}
...
This example - after:
...
.sideblockmain {
}
...
Good luck
Urs