I can't figure out how to change the thumbnail image on a steam workshop item I released this morning, is this possible? 
Dang that’s unfortunate, I don’t even want to make it like an edited thumbnail I just want to add a better image. Thanks anyway capNever found a way, it works for certain games where you can choose the picture ingame but I have yet to find a way for planet zoo. Browsing the workshop from even the big name creators shows zero custom thumbnails.
Yeah I’ve done this but it doesn’t change the actual picture of the item when you’re just scrolling past search results. They only show up when the item is clicked on.Have you gone to the "edit images" section of your workshop item? You can also drag the thumbnails so they are in the order you want them to be in. If you need to, you can add a new photo and drag-n-drop it to the first slot so it's the thumbnail pic.
Hopefully that works