Resolved! Yay!
I do feel like a real idiot now, though, it was so simple...

body {
margin: 0;
padding: 0;
text-align: center;
background: #1F1F1F url(topbg.jpg) repeat-x top;}

I didn't realise I could use an image aswell as a colour. Well, time to move on to content. Thanks again to all those who helped.