[ServiceContract(CallbackContract = typeof(IServiceCallback), 
 SessionMode = SessionMode.Required)]

public interface IService
{
    [OperationContract(IsOneWay = true)]
    void SendData(List<byte> array);
}

public interface IServiceCallback
{
    [OperationContract(IsOneWay = true)]
    void RecieveData(List<byte> array); //this is duplex receiver of image 
}

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession, 
 ConcurrencyMode = ConcurrencyMode.Multiple, 
 MaxItemsInObjectGraph = Int32.MaxValue)]
public class Service : IService
{
    public void SendData(List<byte> array)
    {
        IServiceCallback callback = 
          OperationContext.Current.GetCallbackChannel<IServiceCallback>();
        callback.RecieveData(array);
        //Receiving of message back to user. 
        //It is simple exaple is only to show high duplex performance. 
    }
}

...
<s:Body u:Id="_0"
   xmlns:u="http://docs.oasis-open.org/wss/2004/01/
            oasis-200401-wss-wssecurity-utility-1.0.xsd">
<SendData xmlns="http://tempuri.org/">
<array
xmlns:a="http://schemas.microsoft.com/2003/10/Serialization/Arrays"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
<a:unsignedByte>0</a:unsignedByte>
...
</array>
</SendData>
</s:Body>

...

...
<s:Body u:Id="_0"
xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<SendData xmlns="http://tempuri.org/">
<array>AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=</array>
</SendData>
</s:Body>

...