Yes, you can allow non-members to add their content to your workspace. Simply create a share link that allows for guest upload. To collect images and videos from someone who isn't a member of your workspace, follow these instructions:
Click the "..." button on the board preview and select Share. If you are already within the board, click on Share in the top panel
Within the share window, toggle on Upload to the board
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.
Note: You will always be able to see who contributed each asset by selecting the asset and referencing Creator on the right-side bar, underneath Tags and Boards.
Example: You may want a photographer, freelance designer, or creative agency to have access to a board, but not necessarily an entire workspace. By giving them a share link with upload privileges, your teams can easily share and collaborate.