passing parameters to user control

Question

i would like to pass a parameter to a user control, in order to create a button with a image.

the xaml code should look like this:
<local:ImageButton ImageName="test.png" />

and the object looks something like this:

public string ImageName { get; set; }

public ImageButton() {      
            InitializeComponent();
            this.ImageName = ImageName; 
            this.DataContext = this;       
}

that has a xaml code like this:
<Grid >
<Image  Source="{Binding ImageName}"/>
</Grid>

and now i want to pass the test.png all the way down, so a can create buttons with different images.

i searched for some time, but i could not find something that i could understand. so i holp someone can help me :)