On a personal level, it is obviously the polite thing to do to not post, or to delete if requested, pictures of other people if they (or their parents if they are minors) are not comfortable with it. However, to say that ‘consent’ is required under the GDPR has far-reaching consequences, not least because of the stringent requirements for consent to be valid – e.g. it has to be opt-in, clear, specific and informed.