I do not think you will need to use ajax, you could just use the below and add the image reference to point to the handler in the src.
Please note the image type will need to match your image.
public class MyStreamHandler : IHttpHandler {
public void ProcessRequest (HttpContext context) {
MyServiceClient tcpClient = new MyServiceClient();
Image img = Image.FromStream(tcpClient.GetMyStream(30,100));
img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg)
img.Dispose()
}
public bool IsReusable {
get {
return false;
}
}
}