I am new to Silverlight development. I have created a nice png file in Expression Design. I would like to use this png file as the background for my application. When I set the Stretch property to fill, it does not fill the entire page like I think it should.

Here's the xaml:

<Grid x:Name="LayoutRoot">
    <Grid.Background>
<ImageBrush ImageSource="IgniteTechDesign.png"/>
</Grid.Background>
    <Border x:Name="ContentBorder">

        <navigation:Frame x:Name="ContentFrame" Style="{StaticResource ContentFrameStyle}" 
                          Source="/Home" Navigated="ContentFrame_Navigated" NavigationFailed="ContentFrame_NavigationFailed">
            <navigation:Frame.UriMapper>
              <uriMapper:UriMapper>
                <uriMapper:UriMapping Uri="" MappedUri="/Views/Home.xaml"/>
                <uriMapper:UriMapping Uri="/{pageName}" MappedUri="/Views/{pageName}.xaml"/>
              </uriMapper:UriMapper>
            </navigation:Frame.UriMapper>
        </navigation:Frame>
    </Border>

     <Grid x:Name="NavigationGrid" Style="{StaticResource NavigationGridStyle}">

        <Border x:Name="BrandingBorder" Style="{StaticResource BrandingBorderStyle}">
            <StackPanel x:Name="BrandingStackPanel" Style="{StaticResource BrandingStackPanelStyle}">

                <ContentControl Style="{StaticResource LogoIcon}"/>
                <TextBlock x:Name="ApplicationNameTextBlock" Style="{StaticResource ApplicationNameStyle}" 
                           Text="Application Name"/>

            </StackPanel>
        </Border>

        <Border x:Name="LinksBorder" Style="{StaticResource LinksBorderStyle}">
            <StackPanel x:Name="LinksStackPanel" Style="{StaticResource LinksStackPanelStyle}">

                <HyperlinkButton x:Name="Link1" Style="{StaticResource LinkStyle}" 
                                 NavigateUri="/Home" TargetName="ContentFrame" Content="home"/>

                <Rectangle x:Name="Divider1" Style="{StaticResource DividerStyle}"/>

                <HyperlinkButton x:Name="Link2" Style="{StaticResource LinkStyle}" 
                                 NavigateUri="/About" TargetName="ContentFrame" Content="about"/>

            </StackPanel>
        </Border>

    </Grid>

</Grid>

Thanks in advance.