Tumblr Background code?

-Hi I want to put a background wallpaper for my tumblr blog, but my theme doesn't have an Upload image to background thing, and I really like my theme, but I want to ad a background image, what is the code for it? I found a code but when I use it my background image is really zoomed in I want it to position the image to be stretched not centered so it can fit perfectly... thanks! if there is a way.ybe...



How to put a background image in your Tumblr theme: http://tumblring.net/how-to-put-a-backgr鈥?/a>



Ron