how to set image in textbox in wpf
<TextBox Name="myTextBox" TextChanged="OnTextBoxTextChanged" Width="200">
  <TextBox.Background>
    <ImageBrush ImageSource="TextBoxBackground.gif" AlignmentX="Left" Stretch="None" />
  </TextBox.Background>
</TextBox>

// Create an ImageBrush.
ImageBrush textImageBrush = new ImageBrush();
textImageBrush.ImageSource = new BitmapImage(new Uri(@"TextBoxBackground.gif", UriKind.Relative));
textImageBrush.AlignmentX = AlignmentX.Left;
textImageBrush.Stretch = Stretch.None;
// Use the brush to paint the button's background.
myTextBox.Background = textImageBrush;