Are you looking to change your Myspace backrounds? This is the code for placing the Myspace background image in the top center of the browser window. In order to make the image visible the backgrounds of all the tables in the Myspace layout need to be made transparent. This process will be explained in the Myspace layout tutorials.
background-image:url(http://URL TO IMAGE); background-position: top; background-repeat: no-repeat;
One thing to note is I used only the vertical background-position option and let the default horizontal position of center do its own thing.