The correct sentence which makes use of a PREDICATE NOMINATIVE is option "A": It is them and me in the picture.
A predicate nominative may be a noun or a pronoun that completes the linking verb and renames the subject. We consider the following verbs as linking verbs: the verb to be in all its forms (am, is, are, was, were, be, being, and been) and the sense verbs (taste, smell, sound, look, feel...).