I'm over on XoomForums.com, but for those who haven't ventured over there, I've built a few themes for the Xoom, based on both stock and Rom'd OS'.
Check out Bazar6 Themes for more content and regular updates, as well as any problems, questions or suggestions.
Here's the threads for each theme, and what they're available on:
StockRed: HammerHead 2.1.0, 3G and WiFi 3.1, and Tiamat 1.0
StockGreen: HammerHead 2.1.0, 3G and WiFi 3.1, and Tiamat 1.0
StockGrey: HammerHead 2.1.0, 3G and WiFi 3.1
StockPurple: 3G and WiFi 3.1
You must be rooted to apply these themes.