How to collect images and videos from someone who is not a member of your workspace:
Click the "..." button on any board thumbnail and select Share. If you are already within the board, click on Share in the top panel.
From the Share screen, you will see a few options:
View or View and Upload
View or View and Download
To allow non-members to upload their own images and videos, select View and Upload
Copy and share the link to give access to a contributor. Anyone with this link will now be able to add their own content to the board. They will not have access to any other boards in your workspace unless you create share links for those boards as well.
Video Tutorial: https://www.loom.com/share/e01fd02ba80e4ac5bc7c270917ce9447