Hi Bjorn,
Im having a similar issue with Kiwi Logo Carousel on the Karma theme by True Themes, same company that made the Sterling theme that mkdir is talking about and another user on this post: https://www.ads-software.com/support/topic/images-dont-display-2?replies=3
The images won’t seem to work when you select “Set Featured Image” on an image from your media library or after selecting a file to upload. The logo box just stays blank and you don’t see the logo appearing after file selection.
True Themes seem to be using some kind of custom file dialog which conflicts with some plugins like Kiwi and some other carousels. Kiwi is the best out of all the carousels i tried though so it would be nice to sort this issue out! ??