ScrollViewer with top and bottom shadows to indicate out of view content (requires a MultiValueConverter to compare values).

VerticalScrollViewerStyle.xaml

<Style x:Key="VerticalScrollViewer" TargetType="{x:Type ScrollViewer}">
        <Setter Property="OverridesDefaultStyle" Value="True" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ScrollViewer}">
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition />
                            <ColumnDefinition Width="Auto" />
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition />
                            <RowDefinition Height="Auto" />
                        </Grid.RowDefinitions>
                        <Grid Grid.Row="0" Grid.Column="0">
                            <Border
                                Panel.ZIndex="1"
                                BorderThickness="0"
                                ClipToBounds="True">
                                <Grid>
                                    <Border
                                        Margin="-20,-2,-20,-20"
                                        BorderBrush="Black"
                                        BorderThickness="2">
                                        <Border.Effect>
                                            <DropShadowEffect
                                                BlurRadius="10"
                                                Opacity="1"
                                                ShadowDepth="0" />
                                        </Border.Effect>
                                        <Border.Style>
                                            <Style TargetType="Border">
                                                <Style.Triggers>
                                                    <DataTrigger Value="True">
                                                        <DataTrigger.Binding>
                                                            <MultiBinding Converter="{StaticResource MultiValueEqualityConverter}">
                                                                <Binding
                                                                    ElementName="PART_VerticalScrollBar"
                                                                    Mode="OneWay"
                                                                    Path="Value" />
                                                                <Binding
                                                                    ElementName="PART_VerticalScrollBar"
                                                                    Mode="OneWay"
                                                                    Path="Minimum" />
                                                            </MultiBinding>
                                                        </DataTrigger.Binding>
                                                        <Setter Property="Visibility" Value="Hidden" />
                                                    </DataTrigger>
                                                </Style.Triggers>
                                            </Style>
                                        </Border.Style>
                                    </Border>
                                    <Border
                                        Margin="-20,-20,-20,-2"
                                        BorderBrush="Black"
                                        BorderThickness="2">
                                        <Border.Effect>
                                            <DropShadowEffect
                                                BlurRadius="10"
                                                Opacity="1"
                                                ShadowDepth="0" />
                                        </Border.Effect>
                                        <Border.Style>
                                            <Style TargetType="Border">
                                                <Style.Triggers>
                                                    <DataTrigger Value="True">
                                                        <DataTrigger.Binding>
                                                            <MultiBinding Converter="{StaticResource MultiValueEqualityConverter}">
                                                                <Binding
                                                                    ElementName="PART_VerticalScrollBar"
                                                                    Mode="OneWay"
                                                                    Path="Value" />
                                                                <Binding
                                                                    ElementName="PART_VerticalScrollBar"
                                                                    Mode="OneWay"
                                                                    Path="Maximum" />
                                                            </MultiBinding>
                                                        </DataTrigger.Binding>
                                                        <Setter Property="Visibility" Value="Hidden" />
                                                    </DataTrigger>
                                                </Style.Triggers>
                                            </Style>
                                        </Border.Style>
                                    </Border>
                                </Grid>
                            </Border>
                            <ScrollContentPresenter Panel.ZIndex="0" />
                        </Grid>
                        <ScrollBar
                            x:Name="PART_VerticalScrollBar"
                            Grid.Row="0"
                            Grid.Column="1"
                            Maximum="{TemplateBinding ScrollableHeight}"
                            ViewportSize="{TemplateBinding ViewportHeight}"
                            Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}"
                            Value="{TemplateBinding VerticalOffset}" />
                        <ScrollBar
                            x:Name="PART_HorizontalScrollBar"
                            Grid.Row="1"
                            Grid.Column="0"
                            Maximum="{TemplateBinding ScrollableWidth}"
                            Orientation="Horizontal"
                            ViewportSize="{TemplateBinding ViewportWidth}"
                            Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}"
                            Value="{TemplateBinding HorizontalOffset}" />

                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>