With the absence of VisualBrush in WinRT, I am not sure the approach. Anyone?
At the moment I don't believe there is a way, while ImageBrush inherits from TileBrush it's missing the important property TileMode. It's unclear whether this will be included in later versions.
Indeed there hasn't been much information given in regards to XAML styling WinRT besides changing Dark and Light themes...
so I guess we have to fiddle and experiment...
While doing some googling on the web I came with the following link... might as well give it a shot...
Creating tiled backgrounds in Metro style XAML apps
http://www.robfe.com/2012/07/creating-tiled-backgrounds-in-metro-style-xaml-apps/
Note that it might work in full screen though I ain't sure on how well it responds to snap and rotation.
http://www.mindscapehq.com/ now have a TiledBackground control.
http://www.philliphaydon.com/2013/01/windows-store-app-tiled-background/
<ms:TileBackground ImageSource="/Assets/debut_dark.png" />
Requires a license to access the nightly build.
来源：https://stackoverflow.com/questions/11235813/how-to-tile-a-background-image-in-winrt