When you build a great web site, you need to plan your asset loading so that users don’t get frustrated and leave your website. When you build Windows 8 apps, loading assets is something you have to consider carefully because to publish an app to the Windows 8 store, your app must launch in 5 seconds or less on a low-power computer according to certification requirement 3.8. Asynchronous code is always a good strategy, so is displaying your own splash screen and showing a progress bar as your assets load so the user understands that the program is running and your app is loading assets.
The PreLoadJS library includes (this list is not exhaustive)
There’s a couple of nice demos, such as the preload queue which shows a progress bar that you can check out as well. Download PreLoadJS and find this and other helpful libraries at the CreateJS site. Don’t forget when you publish a Windows 8 app in Canada you can get rewards with Developer Movement, and if you are a student you could enter it in Imagine Cup!