Changing background image from a theme

I am using the itheme2 from themify for our community webpage and can’t figure out why the background image won’t change. Right now, it’s the default dark purple like color. See http://www.eadscolorado.org
I would like to change this. I went to the itheme2 tab on the left, went to settings, then styling, then background image and it says I can upload an image. It then puts in URL in the box right above the upload button and when done uploading and saving these new settings, the background image doesn’t change when I visit the site. It looks like it should be really easy to change from the default to an image since one of the settings is specifically for background image. I even copied the background image I want into the “images” folder where that default purple bg picture is located . Would appreciate any help. A few tutorials said something about some CSS wording/coding but it doesn’t seem like it should be that hard. Thanks!