Creating a Box, and drawing a picture over it?

i am creating a box, trying to color it a certain shade, then put a picture over top of it. but I cant seem to figure out how to do this? basically i want a box with a green background. sort of transparent, then draw a stick man, over top of that green background. in the future i m also going to try to shrink or scale the green background box, but i dont want the image the shrink/scale with it. Sorry for the question, i m still sort of new to unity. this what i have currently:

  public Texture tex;
         GUI.color = new Color(0f,1f,0f,0.4f);
         GUI.Box(new Rect(1250, 10, 250, 150), tex);