With the following code:

``` js
app.on('ready', () => {
    electron.dialog.showMessageBox({
        message: 'Lorem ipsum',
        buttons: [],
        icon: path.join(__dirname, 'Icon.png')
    });
});
```

_The icon is 1024x1024 pixels._

This is what I get on Linux:

<img width="1159" alt="screen shot 2016-05-10 at 18 15 07" src="https://cloud.githubusercontent.com/assets/170270/15144697/4f4d9c1a-16db-11e6-9fd8-a52534a4ae76.png">

The icon is correctly resized on OS X:

<img width="438" alt="screen shot 2016-05-10 at 18 16 03" src="https://cloud.githubusercontent.com/assets/170270/15144718/6ecbac58-16db-11e6-95cc-8c312bcecb2e.png">

And Windows:

<img width="361" alt="screen shot 2016-05-10 at 18 15 37" src="https://cloud.githubusercontent.com/assets/170270/15144721/7432fbe2-16db-11e6-8322-5980def359e9.png">
## 

The documentation for the `icon` option should also document the recommended minimum size for the icon.
## 
- Electron version: 0.37.8
- Operating system: Ubuntu 14.04

atom/browser/ui/message_box_gtk.cc
public:
  GtkMessageBox(NativeWindow* parent_window,
                MessageBoxType type,
                const std::vector<std::string>& buttons,
                int default_id,
                int cancel_id,
                const std::string& title,
                const std::string& message,
                const std::string& detail,
                const gfx::ImageSkia& icon)
      : dialog_scope_(parent_window),
        cancel_id_(cancel_id) {
    
    dialog_ = gtk_message_dialog_new(
        nullptr,  
        static_cast<GtkDialogFlags>(0),