That’s one way to get the style you’re looking for. If your DIV needs to be flexible in all dimensions, then it’s the only way to go. But if you are working with a fixed-width (and variable-height) box, then you can use a single image each as the top and bottom, and a third to create the sides (tiling vertically).
If you let Freeway build this for you, you will get something entirely other – a 9-cell table will be nested inside your DIV to hold the corners in place and to keep the content from crashing into those corners. I don’t recommend this approach personally, because it adds a lot of non-semantic code to your page.
Still another approach is to use my CSS3 Actions to style the box (rounded corners and a shadow can go a long way towards creating a 3D effect).
If you can post a sketch of what you’re trying to accomplish, I could be more help.