Quick example of a custom GUILayout control (untested).

CustomGUILayout.cs

using UnityEngine;

public class CustomGUILayout
{
	public static bool MyFocusControl (Texture2D texture, params GUILayoutOption[] options)
	{
		int id = GUIUtility.GetControlID ();
		Color color = GUI.color;

		GUI.color = GUIUtility.hotControl == id ? Color.green : Color.red;
		Rect rect = GUILayoutUtility.GetRect (texture.width, texture.height, options);

		switch (Event.current.type)
		{
			case EventType.MouseDown:
				if (rect.Contains (Event.current.mousePosition))
				{
					GUIUtility.hotControl = id;
					Event.current.Use ();
				}
			break;
			case EventType.MouseUp:
				if (GUIUtility.hotControl == id)
				{
					GUIUtility.hotControl = 0;
					Event.current.Use ();
				}
			break;
			case EventType.Repaint:
				GUI.DrawTexture (rect, texture);
			break;
		}

		GUI.color = color;

		return GUIUtility.hotControl == id;
	}
}

/*
	Usage:
	
	bool isActive = CustomGUILayout.MyFocusControl (myTexture);
	GUILayout.Label (string.Format ("The custom control is {0}", isActive ? "active" : "inactive"));
*/

It works. Thanks.