The appearance of a particular site has to do with the styling and is controlled through something called CSS (Cascading Style Sheets). In the sample site that you listed, what they did was to set the background property of the heading to an image file, which you can see here:
You didn't specify what WordPress theme you are using, but in general, it is fairly easy to change the CSS. Some themes will come with a Custom CSS option that allows you to enter your own CSS rules. For those that don't, you can use a CSS plugin like Custom CSS Manager to enter your own CSS. However, you should have a basic understanding of CSS if you are planning on making changes to the appearance of your site. There is a good basic tutorial here.