To display larger icons/bitmaps you need to increase the size of the button in the Toolbar. This will in turn increase the size of the image. You can use the MinButtonSize property of the toolbar to achieve this behavior. The default size for the MinButtonSize property is 24 pixels.
To increase the size of the button in the toolbar at design time, complete the following task:
OR
The following toolbar image had a minimum button size that has been increased to 40 pixels: