With Canto, you are able to change the preview of an asset. This is helpful to replace the preview image for, either file that doesn't have a preview image (Zip files) or files that display a low-quality preview due to file conversion  (Ex. TIF Files). 

Note: There are some limitations. The new preview/thumbnail would need to be in PNG, JPG, or JPEG file type. Also, the file size should be 2 MB or less. 

Only image type files must use the same aspect ratio as the original file when replacing the thumbnail. For Video, Audio, Documentation, Presentation, etc are not required to retain the aspect ratio of the original file.

1) Click on the Replace Thumbnail icon and upload an image for the Preview either from Canto or My Selections or the Local Drive. 

2) Select an image from either your Canto library or from your computer and click Ok and you're all set!