Here are some resources that will help you further in developing more compelling UI for your Windows Phone apps:
- Silverlight for Windows Phone Toolkit - contains lots of advance controls to jazz up your app. If you are unsure on how to use them, read here.
- Coding4Fun Toolkit for Windows Phone - more user controls if you are looking to spice up your app further. Read here to learn how to use them.
- Want to do some complex stuff with your phone but don't know where to start? - Checkout the Code Samples for Windows Phone page for everything you need.
- Have a WCF Service but don't know how to call from your UI? - Checkout my post on how to use Silverlight with a Controller & WCF. It will save you a lot of head-ache.
As for Windows 8 Metro Apps, the most puzzling question would be how can you access a WCF back-end? The answer is here. You basically make use of the new Async Programming syntax to call it.
Now what are you waiting for? Go win some prizes! :)