Navigation: Customizing FontCreator > Options >
Options - View
On the Tools menu, click Options, and then click the View tab. Here you can adjust the Font Overview and Glyph Edit Window settings.
Show sample in empty glyphs
Will show a grey sample glyph for empty glyphs in the font overview. You can change the font to use by selecting one from the installed fonts list.
Glyph Edit Window
Here you can set the way a Glyph Edit window will show the glyph