Hi Daysie,
Well, as far as I know, it is not possible to fill polygon graphics with pictures. Although, you may work with marker symbol for points. Here is the snippet from the guide Symbols and renderers—ArcGIS Runtime SDK for Java | ArcGIS for Developers
Image image = new Image("file:RedShinyPin.png");
final PictureMarkerSymbol pictureMarker = new PictureMarkerSymbol(image);
pictureMarker.loadAsync();
pictureMarker.addDoneLoadingListener(new Runnable() {
@Override
public void run() {
Graphic graphic = new Graphic(location, pictureMarker);
graphicsOvelay.getGraphics().add(graphic);
}});
}
Regards,
Adam