A Chinese parts manufacturer offers up a kit to replace iPhone 4 glass panels with transparent ones. Downsides include possible "less than Gorilla" glass strength and transparent glass letting in light for degraded picture quality (same issue with orig. white iPhone 4).
Chris at MICGadget says he will be taking orders:
The transparent back panel I got is a little bit different from the one featured on UWANTS. The one on UWANTS includes the front panel too, while I only have the back panel. And the one I got comes in three colors.
Here're the photograps: