Firebase Cloud Messaging With  push notification with Image 

public class ImageDownload extends AsyncTask<String,Void, Bitmap>{

    @Override
    protected Bitmap doInBackground(String... strings) {

        InputStream inputStream;
        try {
            URL url = new URL(strings[0]);
            try {
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.connect();
                inputStream = connection.getInputStream();
                return BitmapFactory.decodeStream(inputStream);
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }

        return null;
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        ShowNotification(bitmap);
    }
}