The first pic shows the site in VSD. I've set the page background to solid color (white), added my background image in Settings > Add Files, then went to Header > Edit Header and added the CSS code with my .jpg file for the background in it.
http://i38.servimg.com/u/f38/14/58/51/55/vsd-bk10.jpg
This is the result - the patterned background repeats to fill the browser window, and the solid white background fills just the web page. It's not "clickable", it's not a shape/graphic, and it can't be accidentally moved when you're working on other elements

http://i38.servimg.com/u/f38/14/58/51/55/vsd-bk12.jpg
If you look at my site (link below), you'll see I've used this method to put a patterned background (for the browser) under an image background on the actual web pages.
https://www.callendales.com