You would probally need to check out how to modify the css classes to acheive a look you want. Your free to modify the css etc as you need.
Here is a link that explains css
CSS Tutorial
I know some sites use html trickery using images around the actual boxes and some may use css to load images but its mostly the same. Like example changing your menubar class to load a background image with rounded tops which you creat might work for you.