The background image is fine, it looks this way because your slider height is smaller than the demo.
To get it to look like the demo you would have to either increase the height of your slider, or re-create the background image in Photoshop to be shorter. Here is your slider background image – http://savvycities.com/wp-content/themes/optimal/images/slider-bg.png This image repeats itself horizontally (not vertical), but notice where the blue section ends, and the white section begins. The demo slider image is set to 350px which extends itself past the “blue” section of the background slider image.
