Add an image/texture to a custom editorwindow

Hey, I have created a script that opens a pop up window in the editor with 4 buttons that for now, do nothing. This is the script

 using UnityEngine;
 using UnityEditor;
 
 public class AngleSimulator: EditorWindow
 {
 
 
     [MenuItem ("Custom/Tools/AngleSimulator")]
     static void Init () {
 
         AngleSimulator window = (AngleSimulator)EditorWindow.GetWindow (typeof (AngleSimulator));
         window.Show();
     }
 
     void OnGUI ()
   {
     
     if (GUILayout.Button("Start"))
     {
       //rotation = StartAngle
     }
 
     if (GUILayout.Button("End"))
     {
       //rotation = EndAngle
     }
 
     if (GUILayout.Button("Simulate"))
     {
       //slerp(StartAngle, EndAngle)
     }
 
     if (GUILayout.Button("Refresh"))
     {
       //Update
     }
 
     }
 }

And this is how it looks: http://prntscr.com/9iouds

Now I would like to put an image/texture above these 4 buttons , how could I do this? So just that I have like a .jpg file in my assets folder and that it is displayed above the 4 buttons, tyvm!!

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