We intentionally designed dbFront to use jQuery UI. This not only allowed us access to a great set of widgets but also all of the built in themes. The below you will see dbFront cycling through the default jQuery UI themes.
If these themes are not enough then the jQueryUI site has a special ThemeRoller that can be used to quickly role your own custom theme. The URL for their theme roller is: http://jqueryui.com/themeroller/
If that is still not enough then there are also plenty of designers who are capable of building a custom theme.
So you have options.
For instructions on changing the theming in dbFront see: Theme Setup