Windows Phone 8 Splash Screen Requirements

Use of splash screen images is discouraged. Windows Phone 8 applications should start quickly enough so that a splash screen is not required.

If you do use a splash screen for a Windows Phone 8 application, use one of the following naming conventions:

To use...	Do the following...
A single image for all Windows Phone 8 devices	Name the image file SplashScreenImage.jpg. The image should have the dimensions 768x1280px. On devices that have a different screen size, this image will be scaled to fit the screen.
Separate image files for each type of Windows Phone 8 device	Provide multiple image files based on the specific device sizes:
	Image Size	Filename
	480x800px	SplashScreenImage.screen-WVGA.jpg
	768x1280px	SplashScreenImage.screen-WXGA.jpg
	720x1280px	SplashScreenImage.screen-720p.jpg

For more information, refer to information about splash screens on the Microsoft website at http://msdn.microsoft.com/en-us/library/windowsphone/develop/ff769511%28v=vs.105%29.aspx.