<Grid x:Class="Test1.MainBgAd"

             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

             mc:Ignorable="d"  Margin="0" Background="Red"

             d:DesignHeight="300" d:DesignWidth="300">

    <Grid.Resources>

        <Storyboard x:Key="sb1">

            <DoubleAnimation From="0" To ="1" Storyboard.TargetName="img" Storyboard.TargetProperty="Opacity" Duration="0:0:4"></DoubleAnimation>

        </Storyboard>

    </Grid.Resources>

    <Grid>

        <Image Name="imgBg" Stretch="UniformToFill" Opacity="1" Source="/Test1;component/Assets/MianBgAd/minAd2.jpg" />

        <Image Name="img"  Stretch="UniformToFill" Opacity="0" Source="/Test1;component/Assets/MianBgAd/minAd1.jpg" />

    </Grid>

</Grid>

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

using System.Windows.Media.Animation;

namespace Test1

{

    /// <summary>

    /// Interaction logic for MainBgAd.xaml

    /// </summary>

    public partial class MainBgAd : Grid

    {

        public MainBgAd()

        {

            InitializeComponent();

            loadImags();

            sb=Resources["sb1"] as Storyboard;

            sb.Completed += new EventHandler(sb_Completed);

            Loaded += new RoutedEventHandler(MainBgAd_Loaded);

        }

        Storyboard sb;

        int pIndex = 1;

        int MaxIndex = 3;

        List<BitmapImage> imgList = new List<BitmapImage>();

        void MainBgAd_Loaded(object sender, RoutedEventArgs e)

        {

            Start();

        }

         public void Start() {

            sb.Begin();

        }

        void sb_Completed(object sender, EventArgs e)

        {

            if (pIndex > MaxIndex)

            {

                pIndex = 0;

            }

            img.Opacity = 0;

        img.Source=imgList[pIndex];

            if (pIndex - 1 < 0)

            {

                imgBg.Source = imgList[MaxIndex];

            }

            else {

                imgBg.Source = imgList[pIndex - 1];

            }

            sb.Begin();

             pIndex++;

        }

        void loadImags() {

            for (int i = 1; i <= 4; i++)

            {

                imgList.Add( new BitmapImage(new Uri("/Assets/MianBgAd/minAd"+i+".jpg", UriKind.RelativeOrAbsolute)));

            }

        }

    }

}