<UserControl.Resources>
        <Image Source="pack://application:,,,/Resources/someimage.png" Stretch="Fill" OpacityMask="#99FFFFFF" x:Key="MyImage1" />

        <Style TargetType="{x:Type ToggleButton}" x:Key="MyToggleButtonStyle1">
            <Setter Property="Content" Value="{DynamicResource MyImage1}" />
        </Style>
    </UserControl.Resources>

    <!-- .... Далее использование стиля в кнопках контрола .... -->

                <WpfApplication2:UserControl1 x:Name="tlpp1" />

                <WpfApplication2:UserControl1 x:Name="tlpp1" />
                <WpfApplication2:UserControl1 x:Name="tlpp2" />