DockWare is a completely free clock with some very interesting options.
In addition to telling the time, this application displays a background collection of images that fade in and out, which means that when the device is in its cradle, you can see the time, date and any image you want.
One of the most interesting features is the possibility to add new images. Simply convert the photos in question into a resolution of 320x240 and using the ActiveSync Explorer copy them into the directory that contains the application.
An essential clock and image viewer for your device.