Check out the diamond-studded BlackBerry Pearl, available in limited quantities from Amosu...

* A diamond studded Pearl | BlackBerry Cool
* Amosu
* The Boy Genius Report: BlackBerry loves Goooold! - Engadget Mobile


It's pretty unlikely the RIM themselves will make a "premium" BlackBerry device in the foreseeable future, but if you're prepared to pay for it, companies like Amosu will sell you a diamond-studded handset, or convert your existing one...

By the way, they also do a number of other products, including the Apple iPhone and iPod products, and all their products are strictly limited edition.