public class CIMPictureGraphic : CIMGraphic, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

//Create a picture element and also set background and border symbology.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2D envelope geometry
  Coordinate2D pic_ll = new Coordinate2D(6, 1);
  Coordinate2D pic_ur = new Coordinate2D(8, 2);
  //At 2.x - Envelope env = EnvelopeBuilder.CreateEnvelope(pic_ll, pic_ur);
  Envelope env = EnvelopeBuilderEx.CreateEnvelope(pic_ll, pic_ur);

  //Create and add element to layout
  string picPath = @"C:\Temp\WhitePass.jpg";
  //At 2.x - GraphicElement picElm =
  //    LayoutElementFactory.Instance.CreatePictureGraphicElement(
  //                                             layout, env, picPath);
  //         picElm.SetName("New Picture");
  //
  GraphicElement picElm = ElementFactory.Instance.CreatePictureGraphicElement(
                                       layout, env, picPath, "New Picture");

  //(Optionally) Modify the border and shadow 
  CIMGraphic picGra = picElm.GetGraphic();
  CIMPictureGraphic cimPicGra = picGra as CIMPictureGraphic;
  cimPicGra.Frame.BorderSymbol = new CIMSymbolReference();
  cimPicGra.Frame.BorderSymbol.Symbol =
        SymbolFactory.Instance.ConstructLineSymbol(
               ColorFactory.Instance.BlueRGB, 2.0, SimpleLineStyle.Solid);

  cimPicGra.Frame.ShadowSymbol = new CIMSymbolReference();
  cimPicGra.Frame.ShadowSymbol.Symbol =
              SymbolFactory.Instance.ConstructPolygonSymbol(
                    ColorFactory.Instance.BlackRGB, SimpleFillStyle.Solid);

  //Update the element
  picElm.SetGraphic(picGra);
});

// get the current mapview
var mapView = MapView.Active;
if (mapView == null)
  return;

//Valid formats for PictureURL are:
// e.g. local file URL:
// file:///<path>
// file:///c:/images/symbol.png
//
// e.g. network file URL:
// file://<host>/<path>
// file://server/share/symbol.png
//
// e.g. data URL:
// data:<mediatype>;base64,<data>
// data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAU ...
//
// image/bmp
// image/gif
// image/jpeg
// image/png
// image/tiff
// image/x-esri-bglf

var pictureGraphic = new CIMPictureGraphic
{
  PictureURL = @"file:///C:/Images/MyImage.png",
  Box = envelope
};

IDisposable _graphic = mapView.AddOverlay(pictureGraphic);