I used the web builder to make a site. All turned out well! I'm just about 'done' with it, but one problem. My logo at the top is quite small on the mobile version of the site. I have it at max size and tried making the source image larger too, but it still stays at the max size allowed by the web builder. How can I change this to be a true banner that stretches the top of the page, instead of a small rectangle in the center?