This was actually more involved than I thought it would be. I hadn't tried it before. Nothing bad though. Just a few more buttons clicks than I had imagined.

In Page Properties you need to select a solid color background, and set it to black. This will be the background for the page content area. I have the "Centered" check-box checked as well, so the page centers in the browser.

You also need to select the menu item "Settings" > "Background Fill Properties..."

Here you need to select "Solid Color" and pick a color for the border area of the page. It won't actually be used since we're going to replace it with an image, but this trick won't work without Solid Color selected.

Now you need to get your background image into VSD. Use the menu "Settings" > "Add Files..." to copy the image you want to use to the root of your site.

Let's suppose the image is called "border.jpg". This is what your CSS will look like if you want it to just repeat around the border area of the page:

<style type="text/css">
body {
background:url(border.jpg);
}
</style>


That block of code needs to be inserted into the head of the page using the "Edit" > "Edit Header..." menu item I mentioned previously.