Performance of WPF datagrid when using DataGridTemplateColumn

I am using DataGrid to show storagehouse occupancy (Occupied-Show Image With a box, Not Occupied-Show Empty Image).
In DataGrid I am using DataGridTemplateColumn to override the Images.
My Main Form XAML Code:

<xctk:BusyIndicator Name="ctrlBusy" IsBusy="False" BusyContent="Generating Maps..." >
    <Grid>
        <StackPanel>
            <Button Name="btnClick" Grid.Row="0" Click="Button_Click_1" Height="44" VerticalAlignment="Top" 
            HorizontalAlignment="Left" Width="114" Panel.ZIndex="4" Margin="6,3,0,0">Click</Button>

            <StackPanel Orientation="Vertical" Grid.Row="1">
                <TextBlock  Background="SkyBlue" Height="50">

                </TextBlock>
                <DataGrid GridLinesVisibility="None" Background="SkyBlue" 
              BorderBrush="Transparent" IsReadOnly="True" ItemsSource="{Binding}" 
              AutoGenerateColumns="True" AutoGeneratingColumn="dgvMap_AutoGeneratingColumn"   
              CanUserAddRows="False" CanUserSortColumns="true" CanUserDeleteRows="False"  
              HeadersVisibility="Row" Name="dgvMap" SelectionMode="Single" 
              Panel.ZIndex="0" Margin="0,0,0,0" VirtualizingStackPanel.VirtualizationMode="Standard">
                    <!--for removing the blue color bkground default for row selection-->
                    <DataGrid.Resources>
                        <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" 
               Color="Transparent"/>
                    </DataGrid.Resources>
                </DataGrid>
                <TextBlock  Background="SkyBlue" Height="50">

                </TextBlock>
            </StackPanel>
        </StackPanel>
    </Grid>
</xctk:BusyIndicator>

Datatemplate for DataGrid:

 <DataTemplate x:Key="MyDataTemplate" DataType="DataRowView">
        <Grid Background="Transparent">
            <Image Tag="{Binding}" Name="Layer0" Margin="0,0,0,0"  Panel.ZIndex="1"  
                   Width="50" Height="50"   ToolTipService.HasDropShadow="True" ToolTipService.ShowDuration="20000" ToolTipService.InitialShowDelay="200" >
                <Image.ToolTip>
                    <StackPanel>
                        <Label FontWeight="Bold" Background="Blue" Foreground="White" Content="{Binding}" />
                        <TextBlock Padding="10" TextWrapping="WrapWithOverflow" Width="200">
                            This coil is located in this location. Yard Name is FG. Zone is Dispatch Area.
                        </TextBlock>
                        <Line Stroke="Black" StrokeThickness="1" X2="200" />
                        <StackPanel Orientation="Horizontal">
                            <Label FontWeight="Bold">Report to admin in case of coil location mismatch</Label>
                        </StackPanel>
                    </StackPanel>
                </Image.ToolTip>
                <Image.Resources>
                    <Style TargetType="{x:Type Image}">
                        <Setter Property="Source" Value="{Binding Converter={StaticResource IntToImageConverter}, ConverterParameter = Layer0}" />
                        <Style.Triggers>
                            <Trigger Property="IsMouseOver" Value="True">
                                <!-- Hover image -->
                                <Setter Property="Cursor" Value="Hand"/>
                                <Setter Property="Source" Value="C:\Users\Images\Coil3.png"/>
                                <!--<Setter Property="Source" Value="{Binding  Converter={StaticResource HoverImage}}"/>-->
                            </Trigger>
                        </Style.Triggers>
                    </Style>
                </Image.Resources>
            </Image>
        </Grid>
    </DataTemplate>

Main Form Code-Behind:

 private void Button_Click_1(object sender, RoutedEventArgs e)
    {
        btnClick.Content = "Data Loaded";
        Stopwatch sw = new Stopwatch();
        DataTable dt = dbLayer.tblSaddleSelectAll();
        sw.Start();
        dgvMap.ItemsSource = dt.DefaultView;
        sw.Stop();
        btnClick.Content = sw.ElapsedMilliseconds.ToString();

    }



  private void dgvMap_AutoGeneratingColumn(object sender, DataGridAutoGeneratingColumnEventArgs e)
    {
        if (e.PropertyName == "row")
        {
            e.Column.Visibility = System.Windows.Visibility.Hidden;
        }
        var column = new DataRowColumn(e.PropertyName);
        column.Header = e.Column.Header;
        column.CellTemplate = (DataTemplate)Resources["MyDataTemplate"];

        e.Column = column;
    }  

ValueConverter for DataGrid:

public class BoolToImageConverter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        ImageSource result = null;
        var intValue = value.ToString();
        switch (parameter.ToString())
        {
            case "Layer1":
                if (intValue.ToUpper().Contains("EMPTY"))
                {
                    result = null;
                }
                else
                {
                    result = new BitmapImage(new Uri(@"C:\Users\Images\Box3.png"));
                }
                return result;
            default:
                if (intValue.ToUpper().Contains("EMPTY"))
                {
                    //result = null;
                    result = new BitmapImage(new Uri(@"C:\Users\Images\Box1.png"));
                }
                else
                {

                    result = new BitmapImage(new Uri(@"C:\Users\Images\Box2.png"));
                }
                return result;
        }

    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Custom DatagridTemplateColumn:

 public class DataRowColumn : DataGridTemplateColumn
{
    public DataRowColumn(string column) { ColumnName = column; }
    public string ColumnName { get; private set; }
    protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
    {
        var row = (DataRowView)dataItem;
        var item = row[ColumnName];
        cell.DataContext = item;
        var element = base.GenerateElement(cell, item);
        return element;
    }
}

The Data from Database will be like this:

I will be loading maximum of 250 columns, 20 rows from database.
My questions:

1. Is datagrid is best way to show map kind of layouts for the data given range? I need to show presence and absence with some tooltip descriptions.
2. The stopwatch i kept for checking time taken to load DataGrid. It is showing value less than 250ms. But in reality it is taking too much take show and for 4-6 second the UI gets hanged. Why is hanging? How to overcome it? How can i show BusyIndicator till DataGrid is fully created?
3. Is attaching DataTable's DefaultView to DataGrid is better way to do in performance in wise??
4. Is there anything(properties) I missed in DataGrid to improve the performance.