place an image field: mediafield on a form
place next to the image a button, with the same provider: mediafield.
(you need this to make a thumbnail)
make two records with each an image in the mediafield.
if you scroll thru the records, the button shows nicely the same image. so far so good.
make now an empty record, and scroll again. The button, still shows the last viewed image and is not updated in the empty record.!