Eu tenho esse XAML

<ListBox Margin="0,0,-12,0" ItemsSource="{Binding Items}" Name="list">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal" Margin="0,0,0,17">
                <!--Replace rectangle with image-->
                <Image Height="100" Width="100" Source="{Binding Img}" Margin="12,0,9,0"/>
                <StackPanel Width="311">
                    <TextBlock  Text="{Binding Pos}"/>
                </StackPanel>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

No código:

using (IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForApplication())
{
    IsolatedStorageFileStream isoStoreStream = isoStore.OpenFile("chart.xml", FileMode.Open);
    using (StreamReader reader = new StreamReader(isoStoreStream))
    {
        XElement xml = XElement.Parse(reader.ReadToEnd());
        var list = from var in xml.Descendants("Pos")
            select new Single
            {
                Pos = Int32.Parse(var.Attribute("id").Value),
                Img = how read from isolated storage the image id.jpg?
            };

public class Single
{
    public int Pos { set; get; }
    public ??? Img { set; get; }
}

Eu já salvei as imagens no armazenamento isolado, mas o problema é: como posso ler do armazenamento isolado a imagem com nomes como id.jpg (1.jpg, 2.jpg, 3.jpg ...)?