How do I get the GUI Icon to stretch?

post the code you are using to display these and if you are using a guiskin, the relevant details like fixed width/height/stretech/etc (screenshot be best)

I'm not familiar with GUIContent, but it seems fairly limited. Try playing with the GUITexture and GUITexture.pixelInset value ins$$anonymous$$d.

The code is a little convoluted, but I'm using a matrix to resize everything and a GUIskin with its own styles (with fixed height and width set to 0 currently, because they were a headache)

     void OnGUI() {
         GUI.skin = my_skin;
         scale.x = (float)Screen.width/1980.0f;
         scale.y = (float)Screen.height/1080.0f;
         scale.z = 1;
         
         var sv$$anonymous$$at = GUI.matrix;
         GUI.matrix = $$anonymous$$atrix4x4.TRS(Vector3.zero, Quaternion.identity, scale);
         
         if(Event.current.type == EventType.Layout && Event.current.clickCount == 0) 
              GUI.matrix = $$anonymous$$atrix4x4.identity;
         
         if(display_inventory){
             inv_window_rect = GUI.Window(INV_WINDOW_ID, inv_window_rect, InventoryWindow, "", "$$anonymous$$enu Background");
         }
         DisplayToolTip();
         
         GUI.matrix = sv$$anonymous$$at;
     }
     
     public void InventoryWindow(int id){
         GUI.skin = my_skin;
         
         int counter = 0;
         GUI.Box(new Rect(580,250,620,550), "", "Inventory Background");
         for(int y = 0; y < inventory_rows; y++){
             for(int x = 0; x < inventory_cols; x++){
                 if(counter < PlayerScript.Inventory.Count){    
                     GUI.Button (new Rect(411 + (x * button_width + (x*1.5f)), 285 + (y * button_height + (y*5)), button_width, button_height), new GUIContent(PlayerScript.Inventory[counter].material.mainTexture /*PlayerScript.Inventory[counter].ToolTip(PlayerScript.Inventory[counter])*/));
                 } else {
                 counter++;
             }
         }
         SetToolTip();
         GUI.DragWindow();
     }

I think that 'headache' has to be tackled again. You need a GUIStyle to tell your GUIContent how to render and using fixedHeight and fixedWidth to shape the image as you need it, or trying Stretch/true to see if GUI.Button does it automatically) looks to me, from the docs, as the way to do this,.