Hi Melissa

Thanks for posting in the Lucidchart Community! 

When an Admin deletes a user who owns any documents or other assets there will be an option to transfer the user's owned assets to another user. The Admin will be able to enter the email address of the user they'd like to transfer these assets to which in the case of shape libraries will keep these accessible in the Lucidchart account. See screenshot below for the pop-up message an Admin will see when they delete a user. Note that it includes a section specifying number of "Shape Libraries" that the user owns which will be transferred.

Let me know if you have any other questions!