How to add picture to every panel?
All your panels have a common class. Probably .panels. You need to see if your left panels also have a common class, probably .panel-left or something. You can use your browsers element-inspector to see this. It will show you something like this (simplified example) if you select your node that has panels:

&lt;div class="panels"&gt;
  &lt;div class="panel-left"&gt;
    content
  &lt;/div&gt;
&lt;/div&gt;


This gives you a clue where to set your background in CSS.

.panels .panel-left {
  background:url('path/image');
}


You need to find classes that the elements you want to style have in common, but are unique enough so that you style only those.