For more details, see Windows Asset Qualifiers.
Support for Windows 8.1 and Windows Phone SDKs has been deprecated as of SDK 6.3.0.GA and has be removed in SDK 7.0.0.GA.
In order to grant access to pictures library for Windows Phone, you need to provide appropriate Capabilities in your
tiapp.xml. Windows Phone users are prompted to grant or deny permission when your application attempt to use it.