For those of you on Windows Mobile devices and using the classic S2U2 app by XDA member A_C, there are many themes available.
More recently, since the introduction of Android, we have seen more themes based on the popular OS and here are some funky Android clocks by XDA member ayy3um.
The clocks are in 24 hour format, although the XDA member has also provided the A/P/M png files for the clocks in a separate attachment. The clocks come in orange, white and black and the sliders, notification icons, system icons and wallpapers are also available to download.
Additionally included is an Android analog clock by XDA member frambo88.