My Wiki looks ugly, can I change it?
Sure! First, go to Administration, then click Password. Enter your password. Then go to Administration again and click StyleSheetPage. This is where you can set up the style sheet for the site. A lot of people like to hide the top bar (visibility: hidden).
Also, you can upload images and easily include them in your site. Try out stuff and see how it looks.
Visit the CSS Zen Garden site for CSS ideas.