public class StyleParametersConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return StyleParametersConverter.GetValue(parameter as string);
        }
        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return value;
        }
        static Dictionary<string, object> _parameters = new Dictionary<string, object>();
        static StyleParametersConverter()
        {
            // здесь нужно обеспечить "целостность данных"
            // т.е., например, если что-то по каким-то причинам не загрузилось из БД - должны быть добавлены значения по-умолчанию
            _parameters.Add("Button_FontSize", 14);
            _parameters.Add("Button_FontWeight", FontWeights.Bold);
            _parameters.Add("Button_Foreground", Colors.Coral);
            _parameters.Add("TextBlock_Style1_FontSize", 17);
            _parameters.Add("TextBlock_Style1_FontStyle", FontStyles.Italic);
        }
        public static object GetValue(string param_name)
        {
            if (_parameters.ContainsKey(param_name))
                return _parameters[param_name];
            return null;
        }
    }

        <app:StyleParametersConverter x:Key="StyleParametersConverter" />
        <Style TargetType="Button">
            <Setter Property="FontSize" Value="{Binding Converter={StaticResource StyleParametersConverter}, ConverterParameter=Button_FontSize}"/>
            <Setter Property="FontWeight" Value="{Binding Converter={StaticResource StyleParametersConverter}, ConverterParameter=Button_FontWeight}"/>
            <Setter Property="Foreground" Value="{Binding Converter={StaticResource StyleParametersConverter}, ConverterParameter=Button_Foreground}"/>
        </Style>
        <Style x:Key="TextBlockStyle1" TargetType="TextBlock">
            <Setter Property="FontSize" Value="{Binding Converter={StaticResource StyleParametersConverter}, ConverterParameter=TextBlock_Style1_FontSize}"/>
            <Setter Property="FontStyle" Value="{Binding Converter={StaticResource StyleParametersConverter}, ConverterParameter=TextBlock_Style1_FontStyle}"/>
        </Style>

    public sealed class MyConfig : DependencyObject
    {
        static readonly MyConfig _instance = new MyConfig();
        public static MyConfig Instance { get { return _instance; } }

        public static readonly DependencyProperty LabelPaddingProperty = DependencyProperty.Register("LabelPadding", typeof(Thickness), typeof(MyConfig), new UIPropertyMetadata(new Thickness(10)));
        public Thickness LabelPadding { get { return (Thickness)this.GetValue(LabelPaddingProperty); } set { this.SetValue(LabelPaddingProperty, value); } }

        public static readonly DependencyProperty LabelMarginProperty = DependencyProperty.Register("LabelMargin", typeof(Thickness), typeof(MyConfig), new UIPropertyMetadata(new Thickness(10)));
        public Thickness LabelMargin { get { return (Thickness)this.GetValue(LabelMarginProperty); } set { this.SetValue(LabelMarginProperty, value); } }

        public static readonly DependencyProperty LabelFontSizeProperty = DependencyProperty.Register("LabelFontSize", typeof(double), typeof(MyConfig), new UIPropertyMetadata(14.0));
        public double LabelFontSize { get { return (double)this.GetValue(LabelFontSizeProperty); } set { this.SetValue(LabelFontSizeProperty, value); } }
    }

<xxx.Resources>
    <x:Static Member="my:MyConfig.Instance" x:Key="myConfig" />
</xxx.Resources>
...
<Label Padding="{Binding Source={StaticResource myConfig}, Path=LabelPadding}" Margin="{Binding Source={StaticResource myConfig}, Path=LabelMargin}"
        FontSize="{Binding Source={StaticResource myConfig}, Path=LabelFontSize}">
    Text
</Label>

private void Button_Click(object sender, RoutedEventArgs e)
{
    MyConfig.Instance.LabelPadding = MyConfig.Instance.LabelMargin = MyConfig.Instance.LabelPadding.Left > 5 ? new Thickness(5) : new Thickness(10);
    MyConfig.Instance.LabelFontSize += MyConfig.Instance.LabelFontSize < 14 ? 4 : -4;
}