Episode pictures on the APP are different than online

I love the IMDB App. I love the history function showing what I have watched and looked up. A month ago episodes had their own pictures and if they didn’t I uploaded pictures of the episodes in question. But a couple weeks ago all episodes had generic photos on the IOS APP.

I then went on IMDB online and noticed that on the IMDB web page the episodes I searched there had their individual pictures. I then noticed that the episodes that didn’t have pictures on the APP do have them on the web page.

Why is that? I prefer doing my searching on the APP

Thank you