The Contest can be completely customized in its layout, look and feel. However, using the guidelines found here, you can apply your branding and color scheme to the application in a relatively short amount of time. This section provides a workflow walkthrough with everything you need to personalize the creative in your contest.
The stylesheet base.css includes all the paths to the sprites and some images. Once you've edited the image PSD files, upload your new images to your asset folder.
Tip: A Firefox plugin that is very, very highly recommended is Firebug. It allows you to inspect and modify HTML and CSS in the browser and see the results in real time.