Rotating GUI Texture By Angle

Hopefully this works for you, unfortunately I can only really read C# and can't write it so easily so I've written this in unityscript, but maybe you can convert the additions I've made, or possibly unityscript is fine for you...

 var texture : Texture2D = null;
 var angle : float = 0;
 var size : Vector2 = new Vector2(128, 128);
 var pos : Vector2 = new Vector2(0, 0);
 var rect : Rect;
 var pivot : Vector2;
 
 var targetObj : GameObject;
 var screenPos : Vector2;
 var offset : Vector2;
 var Rads : float = 0;
 
 function Start() {
     UpdateSettings();
 }
 
 function Update() {
     screenPos = Camera.main.WorldToScreenPoint(targetObj.transform.position);
     screenPos.y = Screen.height-screenPos.y;
     offset = screenPos - pos;
     Rads = Mathf.Atan2(offset.y, offset.x)-(Mathf.PI/2);
     RadDegConvert(Rads);
 }
 
 function UpdateSettings() {
     pos = new Vector2(transform.localPosition.x, transform.localPosition.y);
     rect = new Rect(pos.x - size.x * 0.5f, pos.y - size.y * 0.5f, size.x, size.y);
     pivot = new Vector2(rect.xMin + rect.width * 0.5f, rect.yMin + rect.height * 0.5f);
 }
 
 function OnGUI() {
     if (Application.isEditor) { UpdateSettings(); }
     var matrixBackup : Matrix4x4 = GUI.matrix;
     GUIUtility.RotateAroundPivot(angle, pivot);
     GUI.DrawTexture(rect, texture);
     GUI.matrix = matrixBackup;
 }
 
 function RadDegConvert(radians) {
     angle = radians*360/(Mathf.PI*2);
 }

hope that works for you,

Scribe