The Real Duckie (who, ages ago, was the first person to join this forum) has created a fancy theme for your iPhone:
"This theme was 2 months in the making. I tried my best, given the limitations, to duplicate the look and feel of Mac OS Leopard. It’s not for everyone, I know, but it was for me and I wanted to share it.
In most cases, I used the exact icon or name for the corresponding app. Some icons have been created specifically with a Mac OS feel to better blend with the rest of the theme (see: ‘Maps’ for a good example). Similarly, some UI Images have been transfered directly from their corresponding App (see: ‘Safari’ buttons). I know it isn’t exact, in some cases, but that’s due to the limitations of the iPhone User Interface. I welcome feedback. This theme is likely to keep evolving, so your questions and suggestions may be sent to duckie @ therealduckie.net (remove spaces around ‘@’ to email)."