On the Home screen, you will see a row showing all of your top-level folders (that the user has permission to see). by default each folder will be represented by a grid of images containing the four most recently uploaded assets in that folder:
Alternatively, you can upload your own image to be shown instead. Just click the three dots at the top right of the folder and click "Upload a cover image". Select an image from your desktop, choose the crop, and you're done. This new image will be visible to all users from now on.
💡 Only admins can change the folder thumbnail
Setting a cover image for a subfolder
In some occasions, sub-folders are shown on the home screen. For example, if a permission group or portal have been configured to only to shown subfolders within a single parent folder, then those subfolders will show on the Home screen.
To set a cover image for a subfolder in this situation:
Log in as an admin
Move the subfolder to the top level
Change its thumbnail using the instructions above
Move the folder back to its original location
Now, that subfolder will show the thumbnail on the Home screen as intended.