As a minimum, we would always suggest that a photographic library has professional indemnity insurance.
When a photographic library holds such a huge collection of images, it’s incredibly difficult to ever be 100% sure on the origin, authenticity and clearances obtained for any image. Unless one person has personally taken all images, which is not the case for most large libraries which have hundreds of contributors.
If a photographic library has employees, it also crucial that you have liability insurance to comply with the law. More often than not, libraries are also considering cyber insurance to protect from hacker attacks on their database and collection. In addition, if you have an office you may wish to insure the office, computers laptops etc.