You can add a custom icon to help identify your shared folders. You can change the logo whenever you want, just as long as your role in the space is an Admin or higher.
To add a custom logo icon:
From your shared folder page in Hub, click Change icon under the name of the space.
In the file picker, select the image icon you want to use from your computer and click Open.
Adjust the size and placement of your image, then click Save to add it to the icon.
To add a cover image for a folder:
Make sure the image you want to use is already in the folder you want to set a cover for.
Open the folder you want to set a cover for.
Hover over the image you want to make the cover image.
Click the three dots on the right of the image and select Set as cover image.