This feature is only available to admins.
Most file formats get a thumbnail preview generated automatically when uploaded to Image Relay, but sometimes that preview is not what you want, and occasionally, it may not load. Or, perhaps you want the thumbnail to display a different page from the uploaded PDF, or a different frame from the uploaded video that is previewed.
To update the thumbnail, locate the asset for which you to change the thumbnail preview.
Click into the asset so you are then in the Details view.
Click the options ellipse in left corner, then Replace Thumbnail.
In the pop-up that appears, click Browse for File then Replace Thumbnails.