I am using DW 4 and have used the method below which was posted in here a couple of years back:
To make the background non-tiling you have to use css.
You can do it from Dreamweaver own menus this way:
1. Do F7 so you get up the CSS Styles menu
2. On the bottom of this menu click the sheet symbol for New Style.
3. In type choose 'Redefine HTML Tag' and in Tag choose 'body'. Click OK.
4. Choose Category 'Background' and browse for your background image.
5. In Repeat choose 'no-repeat' then click OK.
If you are coding yourself you can do it quicker by applying this attribute to your body tag:
<body style="background-image: url(yourimage.gif); background-repeat: no-repeat}">
This is supported by Netscape4/IE4 and up and is a part of the CSS standard.
But am facing a couple of problems:
1). Have tried the method and hit F12 to preview in browser but i don't see the image at all. Sometimes the image appears cropped...
2). Have tried to change to Horizontal and Vertical Positions but to no avail. Image remains in the top left hand corner only.
Furthermore, section like Attachment, Horizontal and Vertical Positions have got an '*' beside it which means: '*Indicates styles not currently diaplayed in Dreamweaver.'