WPF – How to create image button with template

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();
   }
}