Adding an image to both sides of the mainwrapper

This is what my site currently looks like:

This is what I want it to look like: (the image is not to scale)

How do I do this please? I have made the images and added them to my template images. I also added to the stylesheet:

#rightside {
	float: right;
	}
	
#leftside {
	float: left;
	}

I am not sure if I am on the right track or not though. Any help is appreciated.

I have been thinking about it and think I may have come up with a solution of sorts...... Maybe I should just make an image 910 pixels wide and as long as I need it then centre it above the background image somehow? Does that make sense or am I making things harder for myself?

Check post #21 in this thread:

http://www.zen-cart.com/forum/showthread.php?t=102274

It's done with an image with a transparent section the width of your mainWrapper and the other images on the sides.

Thank you Stevesh. Your a wealth of knowledge. My image looks crap lol I will need to make a better one.