The Special menu lets you preview image files so that you can quickly browse pictures on your computer and in your iPhoto or Aperture library. You can preview raw, JPEG, TIFF, PSD, PNG, GIF files, and any other image file that can be opened by QuickTime.
Open the Application Wizard pane in System Preferences and click Menus.
Click the Customize Menus button. In the dialog that appears, click Special.
Click the Customize Previews button. In the Previews panel:
Deselect the "Frame previews" checkbox if you do not want to display previews in a frame.
Drag the Pictures slider to adjust the size of previews.
If you do not see previews in the Special menu, you may have disabled them. To re-enable them, click the Customize Menus button in the Menus pane of the Application Wizard preferences, click Special, and select the "Show previews" checkbox.