Image Field - No thumbnailed images displaying next to add new file

Hi

I have setup my first form and have used the shortcode to load the form in the front end. But my form by default does not display the same as you have on your example page for the image field. The file upload just displays the file name, why is this?

here is my form

and this is your form

https://docs.metabox.io/fields/image-upload/

Thanks

Nick