If the SimpleMarkerOverlay don't have the API about wrapping, that means it don't support that.
But if you only need to add a png as start point and end point, I think you can use other layer to implement that, as below is some code for reference, it only shows the thinking, you can implement your logic based on it.
InMemoryFeatureLayer layer = new InMemoryFeatureLayer();
layer.ZoomLevelSet.ZoomLevel01.DefaultPointStyle = new PointStyle(GeoImage);
LayerOverlay overlay = new LayerOverlay();
overlay.WrappingMode = WrappingMode.WrapDateline;