How to change banner at top of page image?

Technical Details

Forum version : #phpBB2
Position : Founder
Concerned browser(s) : Google Chrome
Who the problem concerns : Yourself

Description of problem

I know you can change it by going into pics management and typing a URL in, but I wish to know how to change it via the CSS section if possible. I want it to be a 3 part single image and I need to put all 3 small images side by side. Right now it is only one, but the only way I can think of to make it 3 side by side as one larger banner would be to alter the CSS section.

How would I go about doing this? I am not extremely experienced with CSS. I know how to change background in CSS but not this banner image.

I changed background by using this at the bottom of the CSS page. Now no matter what images URL I use in pics management, it uses the image I specified in CSS.

Code:

body {
   background-color: #000000;
   background-image: url("http://randomimg.jpg");
        background-repeat: no-repeat;
   background-attachment: fixed;
        background-position: center;
   }

How would I go about changing the banner at the top of the page with the CSS?

I guess it's not going to work in the CSS editor. I have spent 2 hours trying all kinds of things.

I got what I wanted though. I just altered the Overall_Header template to get what I wanted. I did not know about those templates when I asked the question.

Problem solved!