Showing images?

Hi,

I’m working on a website built by someone else. They used Custom Fields Pro to store covers for all their magazines. I’m trying to show these covers on the front end using this plugin but to no avail. ??

This is the shortcode I tried:
[vg_display_data key=”publication_cover”]

On the front-end I now see a number (ID maybe?) but not an image ??
Could you maybe point me in the right direction?

Thanks in advance,
TG