不确定“干净的架构”解决方案，但有一个变通方案可以使用。你可以创建2个Image控件，并在每次迭代中切换它们。
开始时，您将有2个控件，一个可见，一个不可见：

<Grid>
    <Image x:Name="image_1" Stretch="Uniform" />
    <Image x:Name="image_2" Stretch="Uniform" Visibility="Collapsed" />
</Grid>

现在，您可以修改代码，通过更新Visibility在控件之间切换：

private Image _currentImage;
private Image _bufferImage;

public YourControlConstructor()
{
    InitializeComponent();

    // initialize a variables with Image controls
    _currentImage = image_1;
    _bufferImage = image_2;
}

private void UpdateImage(string path)
{
    _bufferImage.Source = null;
    GC.Collect();

    BitmapImage bi = new BitmapImage();
    bi.BeginInit();
    bi.CacheOption = BitmapCacheOption.OnLoad;
    bi.UriSource = new Uri(path);
    bi.EndInit();
    bi.Freeze();

    _bufferImage.Source = bi;

    // exchange variables to know which image is currently displayed
    Image temp = _currentImage;
    _currentImage = _bufferImage;
    _bufferImage = temp;

    // Update visibility to change images
    _currentImage.Visibility = Visibility.Visible;
    _bufferImage.Visibility = Visibility.Collapsed;

    GC.Collect();
    delete_old(path);
}