You get this result because default rendering calls ToString()
on the item, which prints the name of the class. If you want to display the image you have to supply an ItemTemplate
:
<FlipView x:Name="flpView" Grid.Row="1" Margin="10, 10, 10, 10">
<FlipView.ItemTemplate>
<DataTemplate>
<Image Stretch="UniformToFill" Source="{Binding}" />
</DataTemplate>
</FlipView.ItemTemplate>
</FlipView>