There's still no property with which you could change the orientation of the RadTileViewItem header, but you can achieve this bye editing the default template. The project the my colleague has attached doesn't work properly with the newest dlls because it was created with Q3 2010 dlls and there has been some changes to the default template in the Q1 2011.
For further references could you please examine the attached project and if you have more questions feel free to ask.
All the best,
the Telerik team
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