Taken from http://www.cshtml5.com/links/limitations.aspx
ImageBrush is not yet supported.
Workaround: use an <Image> control instead. If you need to place the <Image> control behind another control, you can do so by placing both the <Image> control and the said control inside a surrounding <Grid> control. Here is an example of use of the Image control: <Image Source="/AssemblyName;component/FolderName/ImageFileName.jpg" Width="320" Height="240"/>