If I delete a member that we no longer employ from my space, will I still see all the issues and wikis that they created/modified? And will their name and image still be shown in the created/modified/assigned fields?
Welcome to our Community!
Yes, if you delete the member from your space (Organization settings), you can still see all the issues and wikis that they have created or edited.
Their name will still be shown in the created/modified/assigned fields, but their profile image will be gone/replaced by a generic image, e.g. like this one:
In summary, the records of their activity in Backlog are kept.