在透明背景的isSelected上改变TabItem图像背景

<TabControl>
    <TabControl.Resources>
        <Style TargetType="TabItem">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="TabItem">
                        <Grid>
                            <Image Source="/Images/DefaultBackground.png"/> <!-- 默认的背景图像 -->
                            <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/> <!-- 显示内容 -->
                        </Grid>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsSelected" Value="True">
                                <Setter TargetName="BackgroundImage" Property="Source" Value="/Images/SelectedBackground.png"/> <!-- 选中时的背景图像 -->
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </TabControl.Resources>
    
    <TabItem Header="Tab 1">
        <!-- Tab 1 内容 -->
    </TabItem>
    <TabItem Header="Tab 2">
        <!-- Tab 2 内容 -->
    </TabItem>
</TabControl>