Place a button on the front panel, select it, go "Edit..Customize control". In the control editor, import a picture using "Edit..Import picture from file" (or simply copy an image to the clipboard).
Now right-click on the button and select "Import picture". You can either import seperate picture for the true and false case or import the image as decal.
Close the control editor and you'll have the option to save the custom control and also to replace the control in the original VI with the new version.
For more details see the section labeled "Importing Graphics into Boolean Controls and Indicators" in the online help and
Application note 159: LabV
IEW� Custom Controls, Indicators,
and Type Definitions .