Show/Hide the DropDown Elements when you Open/Close the DropDown

I came across a requirement that needed the silverlight dropdown to show an image, only when the item has been selected after the dropdown has been closed. I have, however, showed an image with a label that shows a small description.
The code is given here:

<combobox x:name="cmbTest" itemssource="{..}" selectedvaluepath=".." width="52" selectedvalue="{Binding }">

   <ComboBox.ItemTemplate>

      <DataTemplate>

            <StackPanel Orientation="Horizontal">

               <Image Grid.Row="1" Margin="0,0,4,0" Source="{Binding image}" Width="25" Height="25" />

               <TextBlock Text="{Binding YourProperty}" Margin="0,0,4,0" Visibility="{Binding Path=IsDropDownOpen,

                     ElementName=cmbTest, Converter={StaticResource BoolToVisibilityConverter}}" />

            </StackPanel>

         </DataTemplate>

   </ComboBox.ItemTemplate>

</combobox>