Does a public photograph remove the right to privacy?
No. Publishing a photograph permits people to view and discuss what was intentionally disclosed; it does not authenticate every rumour attached to it. Visibility is not unlimited consent, and public interest is not identical to public curiosity.
Can Muslims question the religious validity of the marriage?
They can explain Islamic principles in general terms. They cannot honestly determine the ruling on this particular marriage without verified knowledge of the parties’ faith, the legal and religious process followed, and any circumstances unknown to social media.