<Button>
    <Button.Template>
        <ControlTemplate TargetType="Button">
            <Grid>
                <Image Source="pic.png" Stretch="None" />
                <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center">Operation</TextBlock>
            </Grid>
        </ControlTemplate>
    </Button.Template>
</Button>

<Button>
    <Button.Template>
        <ControlTemplate TargetType="Button">
            <Grid>
                <Image Source="pic.png" Stretch="None" />
                <TextBlock Text="Operation" VerticalAlignment="Center" HorizontalAlignment="Center">
                    <TextBlock.LayoutTransform>
                        <RotateTransform Angle="-90" />
                    </TextBlock.LayoutTransform>
                </TextBlock>
            </Grid>
        </ControlTemplate>
    </Button.Template>
</Button>