The following example shows a style for the CheckBox control:
<Style x:Key="{x:Type CheckBox}" TargetType="CheckBox">
<Setter Property="SnapsToDevicePixels" Value="true"/>
<Setter Property="OverridesDefaultStyle" Value="true"/>
<Setter Property="FocusVisualStyle" Value="{StaticResource CheckBoxFocusVisual}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="CheckBox">
<BulletDecorator Background="Transparent">
<BulletDecorator.Bullet>
<Border x:Name="Border"
Width="13"
Height="13"
CornerRadius="0"
Background="{StaticResource NormalBrush}"
BorderThickness="1"
BorderBrush="{StaticResource NormalBorderBrush}">
<Path
Width="7" Height="7"
x:Name="CheckMark"
SnapsToDevicePixels="False"
Stroke="{StaticResource GlyphBrush}"
StrokeThickness="2"
Data="M 0 0 L 7 7 M 0 7 L 7 0" />
</Border>
</BulletDecorator.Bullet>
<ContentPresenter Margin="4,0,0,0"
VerticalAlignment="Center"
HorizontalAlignment="Left"
RecognizesAccessKey="True"/>
</BulletDecorator>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="false">
<Setter TargetName="CheckMark" Property="Visibility" Value="Collapsed"/>
</Trigger>
<Trigger Property="IsChecked" Value="{x:Null}">
<Setter TargetName="CheckMark" Property="Data" Value="M 0 7 L 7 0" />
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter TargetName="Border" Property="Background" Value="{StaticResource DarkBrush}" />
</Trigger>
<Trigger Property="IsPressed" Value="true">
<Setter TargetName="Border" Property="Background" Value="{StaticResource PressedBrush}" />
<Setter TargetName="Border" Property="BorderBrush" Value="{StaticResource PressedBorderBrush}" />
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter TargetName="Border" Property="Background" Value="{StaticResource DisabledBackgroundBrush}" />
<Setter TargetName="Border" Property="BorderBrush" Value="{StaticResource DisabledBorderBrush}" />
<Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
For more information about this example, see CheckBox ControlTemplate Example.