Your second set of sentences is right, but a bit awkward. The first set needs changing. The easiest and most natural way to say what you want while pointing at the picture: This is us. This is them. (Or “That is them” can work as a contrast to “this is us.”) Is this you?

If the picture is near to you, you can say "this is us". If the picture is far then you can say, "that is us". "this is us or that is us" if you wanted to say that it is you together with other people inside the picture

If it is singular(picture) you say: This is ours(not us). If it is plural (pictures) you say: These are ours(not us). -"ours" is a possessive pronoun while "us" is an object pronoun which is used after a main verb. - Are these yours(not you)? Yours is possessive pronoun while you is object pronoun. The last three sentences are grammatically and semantically incorrect.

@nada: I have a question. What if she means that they are in the picture? I mean, she wants to say that the people in the picture are they. Is it correct to say, this is us?