Changing array of display images with other set of images on user button press event

Hey all,

I am working on developing an random event based game and using Unity5.5.1f1. Where user have to click on image and see if the given image is already present in a grid or not.I want to make it more interesting after each selection these 6 image shown to user should change. My current code is -

public void BuildList()

  {

      GUILayout.BeginHorizontal();

      while (score < finalScore)

      {

          foreach (Card card in cardShow)

          {

              if (GUILayout.Button(Resources.Load(card.Name)  as Texture, GUILayout.Width(100)))

              {

                  Debug.Log("image clicked " + card.Name);

                  int res = Coordinate(card.Name);

                  Debug.Log("loc in arr " + res);

                  if (res != -1)

                  {

                      int cl = res % 3;

                      int rw = res / 3;

                      score += (rw + 1);

                      Debug.Log("col " + cl + " row " + rw);

                      Card cd = aGrid[rw, cl];

                      cd.Name = card.Name;

                      GUILayout.Box(Resources.Load(cd.Name) as Texture, GUILayout.Height(100), GUILayout.Width(100));

                  }

                  else

                  {

                      score += res;

                  }

                  Wait();

                  Debug.Log("score " + score);

              }

          }

      }

      GUILayout.EndHorizontal();

  }

I want the image which are shown to user should change after each click. When I try to do in OnGuI by calling this function by randomizing cardShow array it shows new 6 image side by side. But I want it to draw new images on previous shown array of image But when i choose to blank the screen by

      GUILayout.BeginArea(new Rect(0, 0, Screen.width, Screen.height));

   //   UnityEngine.UI.Graphic.SetAllDirty();

      GUILayout.EndArea();

It shows a blank screen but didn't redraw and task manager shows processor getting eaten up.