decoration:
BoxDecoration(
  color: const Color(0xff7c94b6),
  image: new DecorationImage(
    fit: BoxFit.cover,
    colorFilter: 
      ColorFilter.mode(Colors.black.withOpacity(0.2), 
      BlendMode.dstATop),
    image: new NetworkImage(
      'http://www.server.com/image.jpg',
    ),
  ),
),