ControlTemplate를 이용한 버튼 예제.

<Button Width="100" Height="100" Content="안녕하세요" FontSize="15" Click="Button_Click">
            <Button.Template>
                <ControlTemplate>
                    <Grid>
                        <Ellipse Width="100" Height="100">
                            <Ellipse.Fill>
                                <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
                                    <GradientStop Offset="0" Color="Blue"></GradientStop>
                                    <GradientStop Offset="1" Color="Red"></GradientStop>
                                </LinearGradientBrush>
                            </Ellipse.Fill>
                        </Ellipse>
                        <Ellipse Width="80" Height="80">
                            <Ellipse.Fill>
                                <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
                                    <GradientStop Offset="0" Color="White"></GradientStop>
                                    <GradientStop Offset="1" Color="Transparent"></GradientStop>
                                </LinearGradientBrush>
                            </Ellipse.Fill>
                        </Ellipse>
                        <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
                    </Grid>
                </ControlTemplate>
            </Button.Template>
        </Button>