import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
...
StackPane root = new StackPane();
Image image1 = new Image("image.jpg");
ImageView iv = new ImageView();
iv.setImage(image1);
root.getChildren().add(iv);
primaryStage.setScene(new Scene(root, 300, 250));
primaryStage.show();