If you have the Edit Assets' Metadata, Type, and Preview permission, you can upload alternate previews of assets that do not have previews. Uploading alternate previews allows others to know what assets look like and determine whether or not to download or share them. Upload any file format as an alternate preview, although for something like compressed archives, we recommend that you upload images. Videos can be used as alternate previews, but processing may take some time before the preview displays.
Upload Alternate Previews
To upload an alternate preview, click Upload Alternate Preview on the Asset Details page. Files for previews that are not automatically created will be uploaded.
Alternate previews can be removed after they've been uploaded by clicking Remove Alternate Preview on the Asset Details page.