Assuming that you have read about and are using the override system and have created your own template & folder the images are placed here:
includes/templates/your_template/images/
Depending on the exact type of graphic, the entries can all be in the stylesheet.css file. Example for the side boxes:
Code:
.leftBoxHeading, .rightBoxHeading {
margin: 0em;
background-image:url(../images/your_graphic.gif_or_jpg);
background-repeat:no-repeat;
padding: 0.5em 0.2em;
}
for the center area:
Code:
.centerBoxHeading {
margin: 0em;
background-image:url(../images/your_graphic.gif_or_jpg);
background-repeat:no-repeat;
padding: 0.5em 0.2em;
}
and so forth.. If you are not using FireFox and the web tools extention or another tool to determine the class of the items you are trying to add these to I suggest that you consider getting one of them and FF is free.
Also, looking at your site, it is similar to the "Future Zen: free template that is in the downloads under templates. and you can view them here:Template Test Drive to match your old site exactly you would require your graphics or some modification to the Future Zen to eliminate the side borders and bottom border. This would provide you with most all the required coding and is all css based.