Display images in tool tips and buttons

Hey everyone! I have a button with 3 images(up,hover,clicked). I am using a GUI skin to switch between the 3. I also need to make a tool tip appear when the user hovers over the button, which also needs to be an image. Every example I have seen only does simple strings. I have 12 buttons that need this. So far I managed to access it if I just call the normal button of the skin, but not using the custom skins. I also can't get it to display the tool tip image. It will display if I give it a string, but the image gets put on the button instead.

  if(GUI.Button (new Rect(100,100,100,100), new GUIContent("", toolTipImage), "growthBtn"))
                     {
                         do stuff;
                     }
                     GUI.Label(new Rect(110,110,290,132), GUI.tooltip);