You don't need an initializer, unless you're dynamically loading a different image each time. I think doing as much as possible in fxml is more organized. Here is an fxml file that will do what you need.
<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import javafx.scene.image.*?>
<?import javafx.scene.layout.*?>
<AnchorPane
xmlns:fx="http://javafx.co/fxml/1"
xmlns="http://javafx.com/javafx/2.2"
fx:controller="application.SampleController"
prefHeight="316.0"
prefWidth="321.0"
>
<children>
<ImageView
fx:id="imageView"
fitHeight="150.0"
fitWidth="200.0"
layoutX="61.0"
layoutY="83.0"
pickOnBounds="true"
preserveRatio="true"
>
<image>
<Image
url="src/Box13.jpg"
backgroundLoading="true"
/>
</image>
</ImageView>
</children>
</AnchorPane>
Specifying the backgroundLoading property in the Image tag is optional, it defaults to false. It's best to set backgroundLoading true when it takes a moment or longer to load the image, that way a placeholder will be used until the image loads, and the program wont freeze while loading.