All of this can easily be acheived in the xaml by adding the following code in the grid
<Grid>
<Grid.Background>
<ImageBrush ImageSource="/MyProject;component/Images/bg.png"/>
</Grid.Background>
</Grid>
Left for you to do, is adding a folder to the solution called ‘Images’ and adding an existing file to your new ‘Images’ folder, in this case called ‘bg.png’