Importing image file as thumbnail of an asset

You must be assigned with Change Thumbnail Rights role to change the thumbnail of an asset.
The image file must not exceed 128KB in size.
Image file formats such as JPG, PNG, TIF, and GIF are supported.

You can import an external image and set it as the thumbnail of an asset.

Select an asset in the Asset List.
Right-click on the asset and select Upload Thumbnail.
The Select Thumbnail File dialog opens.
Browse and select an image to import as the new thumbnail.
Click Open.

The new thumbnail replaces the previous thumbnail of the asset.