Just remove first backslash:
<Grid>
<Button Width="75" Height="50" Click="Button_Click">Push Me</Button>
<Image HorizontalAlignment="Left" Height="100" Margin="289,460,0,0" VerticalAlignment="Top" Width="100">
<Image.Source>
<BitmapImage UriSource="Images/atlantafalcons.jpg" />
</Image.Source>
</Image>
</Grid>