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

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    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="ContentControl" x:Key="ContentControlStyle">
        <Setter Property="Foreground" Value="{x:Null}"/>
        <Setter Property="Background" Value="{x:Null}"/>
        <Setter Property="BorderBrush" Value="{x:Null}"/>
        <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="ContentControl">
                    <ContentPresenter
                        Content="{TemplateBinding Content}"
                        ContentTemplate="{TemplateBinding ContentTemplate}"
                        ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
                        HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                        VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                        Margin="{TemplateBinding Padding}"/>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style TargetType="map:MapContentControl" BasedOn="{StaticResource ContentControlStyle}"/>

    <Style TargetType="map:MapItem" BasedOn="{StaticResource ContentControlStyle}"/>

    <Style TargetType="map:Pushpin" BasedOn="{StaticResource ContentControlStyle}">
        <Setter Property="HorizontalAlignment" Value="Center"/>
        <Setter Property="VerticalAlignment" Value="Bottom"/>
        <Setter Property="HorizontalContentAlignment" Value="Center"/>
        <Setter Property="VerticalContentAlignment" Value="Center"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="CornerRadius" Value="0"/>
        <Setter Property="Padding" Value="4,6"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="map:Pushpin">
                    <map:PushpinBorder
                        HorizontalAlignment="{TemplateBinding HorizontalAlignment}"
                        Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderWidth="{Binding BorderThickness.Left, RelativeSource={RelativeSource TemplatedParent}}"
                        CornerRadius="{TemplateBinding CornerRadius}"
                        Padding="{TemplateBinding Padding}">
                        <ContentPresenter
                            Content="{TemplateBinding Content}"
                            ContentTemplate="{TemplateBinding ContentTemplate}"
                            ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
                            HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                            VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                    </map:PushpinBorder>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>