XAML-Map-Control/MapControl/UWP/Themes/Generic.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:map="using:MapControl">
    <Style TargetType="map:MapItemsControl">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate>
                    <ItemsPresenter/>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="ItemsPanel">
            <Setter.Value>
                <ItemsPanelTemplate>
                    <map:MapPanel/>
                </ItemsPanelTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style TargetType="map:MapItem">
        <Setter Property="HorizontalAlignment" Value="Stretch"/>
        <Setter Property="VerticalAlignment" Value="Stretch"/>
        <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
        <Setter Property="VerticalContentAlignment" Value="Stretch"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="map:MapItem">
                    <ContentPresenter Content="{TemplateBinding Content}"
                                      ContentTemplate="{TemplateBinding ContentTemplate}"
                                      ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
                                      Margin="{TemplateBinding Padding}"
                                      HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                      VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style TargetType="map:Pushpin">
        <Setter Property="HorizontalAlignment" Value="Left"/>
        <Setter Property="VerticalAlignment" Value="Bottom"/>
        <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
        <Setter Property="VerticalContentAlignment" Value="Stretch"/>
        <Setter Property="Padding" Value="3"/>
        <Setter Property="Foreground" Value="Black"/>
        <Setter Property="Background" Value="White"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="map:Pushpin">
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition/>
                            <RowDefinition Height="Auto"/>
                        </Grid.RowDefinitions>
                        <Rectangle Fill="{TemplateBinding Background}"/>
                        <Path Grid.Row="1" Fill="{TemplateBinding Background}" Data="M 0,-0.5 L 0,16 16,-0.5"/>
                        <ContentPresenter Content="{TemplateBinding Content}"
                                          ContentTemplate="{TemplateBinding ContentTemplate}"
                                          ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
                                          Margin="{TemplateBinding Padding}"
                                          HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                          VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>