Scaling Background Image

I just started with my blog and am still hosting it on WordPress. I’ve made all the changes I want by simply editing the CSS (I’m using Twenty Eleven).

Except for one… Getting the background image, which is pretty much just a header, to scale to fit the window. I’ve tried a bunch of different variations of code to no avail. I’ve read that this is only possible if the image is in the host location, but I’m trying real hard to find a way around it.

This is what I have at the moment, which works for the built-in header:

#page {
    background: url(http://i1170.photobucket.com/albums/r530/jhgonzalez7/Blog%20Banner%20copy_zps5cb9d6ad.jpg) no-repeat, #FFFFFF;
    width: 100%;
    height: auto;
}

If anyone would be able to help me avoid hosting this myself I would be sooo thankful!