Margin Images

[fanhockeycoach]

I want to put a picture along the margins on my site. Is there a way to keep the main body of my page centered no matter how big the window is? if i set the margin to picture size then the main content doesn't stay center, if i leave it to auto margin then the main body is centered but then the image in the margin gets moved behind body. help

site is fhahockey.com

also is there a way to get the same image on both sides of the margin?