Am I responsible for arranging the copyright in images that someone else offers me?

If you want to reuse images offered by another party, you have to ensure that the provider owns all copyrights in the work.

If you want to use this work in your own production with significant financial interests, it is advisable to ask the provider of the work for a so-called warranty declaration. In such a declaration, the provider declares that it owns the copyrights in the materials and/or that it indemnifies you against all claims others may assert against the materials.