With IMDB on display, click on the site identity button and then on More Information. This will open up the page info dialog.

First select the Permissions panel, make sure that "Load Images" is set to allow (selecting Use Default should also work)

Next select the Media panel, then click on the first item in the list. Use the down arrow key to scroll through the list. If any item has the option "Block images from (domain name)" selected, de-select the option.

This should hopefully resolve your issue, but also see Fix problems that cause images to not show.

You were VERY close but I discovered it was an issue with Adblock. Images were turned off for IMDB (which I'd never have looked at without your post) so I enabled all things IMDB and everything worked out.

Thanks!