publicclass CustomRadPictureBox : RadPictureBox
{
    protected override RadPictureBoxElement CreateImageEditorElement()
    {
        return new CustomPictureBoxElement();
    }

    public override string ThemeClassName
    {
        get { return typeof(RadPictureBox).FullName; }
        set { base.ThemeClassName = value; }
    }
}

public class CustomPictureBoxElement : RadPictureBoxElement
{
    protected override Type ThemeEffectiveType
    {
        get { return typeof(RadPictureBoxElement); }
    }
    protected override PictureBoxCanvasElement CreateCanvasElement()
    {
        return new MyPictureBoxCanvasElement(this);
    }

    public class MyPictureBoxCanvasElement : PictureBoxCanvasElement
    {
        public MyPictureBoxCanvasElement(RadPictureBoxElement owner) : base(owner)
        {
        }

        public override SizeF PositionOffset
        {
            get { return base.PositionOffset; }
            set { base.PositionOffset = TelerikDpiHelper.DescaleSizeF(value, this.DpiScaleFactor); }

        }
    }
}