public class PresentationElementFactory : IPresentationElementFactory  

//Must be on QueuedTask
await QueuedTask.Run(() =>
{
  //create a picture element
  var imgPath = @"https://www.esri.com/content/dam/esrisites/en-us/home/" +
   "homepage-tile-podcast-business-resilience-climate-change.jpg";

  //Build a geometry to place the picture
  Coordinate2D ll = new Coordinate2D(3.5, 1);
  Coordinate2D ur = new Coordinate2D(6, 5);
  Envelope env = EnvelopeBuilderEx.CreateEnvelope(ll, ur);
  //create a picture element on the page
  var gElement = PresentationElementFactory.Instance.CreatePictureGraphicElement(page, env, imgPath);

  //create a text element
  //Set symbology, create and add element to a presentation page
  CIMTextSymbol sym = SymbolFactory.Instance.ConstructTextSymbol(
                ColorFactory.Instance.RedRGB, 15, "Arial", "Regular");
  //use ElementInfo to set placement properties
  var elemInfo = new ElementInfo()
  {
    Anchor = Anchor.CenterPoint,
    Rotation = 45
  };
  string textString = "My text";
  var textPos = new Coordinate2D(5, 3).ToMapPoint();
  var tElement = PresentationElementFactory.Instance.CreateTextGraphicElement(page,
    TextType.PointText, textPos, sym, textString, "telement", false, elemInfo);

  //create a group element with elements created above
  var elmList = new List<Element> { gElement, tElement };
  GroupElement grp1 = PresentationElementFactory.Instance.CreateGroupElement(page, elmList, "My Group");
});