BarManager.ToolbarGlyphSize Attached Property
Gets or sets whether a small or large image is displayed by bar item links within bars that belong to the current bar manager. This is a dependency property.
A GlyphSize value that specifies whether a small or large image is displayed by corresponding bar item links.
If the ToolbarGlyphSize property is set to Default, and bar items in a toolbar have both a large and small images assigned, a large image will be displayed. Set the ToolbarGlyphSize property to Small, to display bar item links using large images.
See the BarItem.Glyph property to learn more.