WPF - How to create image button with template

Question

You won't need dependency properties because you are inheriting from Button. You already have the IsPressed and IsEnabled properties. In fact, this is all you need:

<Button x:Class="TestWpfApplication.ThreeStateImageButton"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
   <Button.Template>
      <ControlTemplate TargetType="{x:Type Button}">
         <Grid>
            <Image Name="Normal" Source="Resources/Normal.png"/>
            <Image Name="Pressed" Source="Resources/Pressed.png" Visibility="Hidden"/>
            <Image Name="Disabled" Source="Resources/Disabled.png" Visibility="Hidden"/>
         </Grid>
         <ControlTemplate.Triggers>
            <Trigger Property="IsPressed" Value="True">
               <Setter TargetName="Normal" Property="Visibility" Value="Hidden"/>
               <Setter TargetName="Pressed" Property="Visibility" Value="Visible"/>
            </Trigger>
            <Trigger Property="IsEnabled" Value="False">
               <Setter TargetName="Normal" Property="Visibility" Value="Hidden"/>
               <Setter TargetName="Disabled" Property="Visibility" Value="Visible"/>
            </Trigger>
         </ControlTemplate.Triggers>
      </ControlTemplate>
   </Button.Template>
</Button>

With your UserControl code-behind file:

public partial class ThreeStateImageButton : Button
{
   public ThreeStateImageButton()
   {
      InitializeComponent();
   }
}

I have provided an alternative to this solution, its not quite as light weight but it offers much greater re-usability.

WPF TriState Image Button

 public static readonly DependencyProperty DefaultImageSourceProperty = DependencyProperty.Register("DefaultImageSource", typeof(ImageSource), typeof(PressedImageButton), new PropertyMetadata(null, new PropertyChangedCallback(DefaultImageSourceChangedCallback)));
    public static readonly DependencyProperty PressedImageSourceProperty = DependencyProperty.Register("PressedImageSource", typeof(ImageSource), typeof(PressedImageButton), new PropertyMetadata(null, new PropertyChangedCallback(PressedImageSourceChangedCallback)));
    public static readonly DependencyProperty ImageStretchProperty = DependencyProperty.Register("ImageStretch", typeof(Stretch), typeof(PressedImageButton), new PropertyMetadata(Stretch.None, new PropertyChangedCallback(ImageStretchChangedCallback)));

---

   <ControlTemplate>
        <Grid>
            <Image Name="imgDefault" Source="{Binding Path=DefaultImageSource,ElementName=uc}" Stretch="{Binding Path=ImageStretch,ElementName=uc}"></Image>
            <ContentPresenter Content="{TemplateBinding Property=ContentControl.Content}" />
        </Grid>
        <ControlTemplate.Triggers>
            <Trigger Property="Button.IsPressed" Value="True">
                <Setter Property="Image.Source" TargetName="imgDefault" Value="{Binding Path=PressedImageSource,ElementName=uc}"></Setter>
                <Setter Property="UIElement.Effect">
                    <Setter.Value>
                        <DropShadowEffect BlurRadius="10" Color="Black" Direction="0" Opacity="0.6" RenderingBias="Performance" ShadowDepth="0" />
                    </Setter.Value>
                </Setter>
            </Trigger>
            <Trigger Property="Button.IsMouseOver" Value="True">
                <Setter Property="UIElement.Effect">
                    <Setter.Value>
                        <DropShadowEffect BlurRadius="10" Color="White" Direction="0" Opacity="0.6" RenderingBias="Performance" ShadowDepth="0" />
                    </Setter.Value>
                </Setter>
            </Trigger>
        </ControlTemplate.Triggers>
    </ControlTemplate>