I agree that the Russian behavior in this matter is execrable.
Still, it is not right to make this display and the ends in view could easily have been achieved by proper communications through legitimate channels.
There is nothing preventing the Ukrainian government from informing their families through the Red Cross, of making a complaint to the UN, NATO and all interested governments, and issuing press releases correctly identifying the prisoners. This could include ID type pictures of the men posed with dignity.
I think the primary purpose was to put the lie to the claim that Russia has not invaded Ukraine. As to the question of privacy, the soldiers in the photos do not look pleased at having been captured, but do not appear mistreated. The photos themselves are not mocking or humiliating, something that would violate the Geneva convention. Having seen enough videos of Ukrainian troops captured, tortured and interrogated by Russian soldiers and journalists, these photos do not appear to cross the line. Perhaps the barbaric behavior of Lifenews journalists insulting and mistreating Ukrainian soldiers has colored my perception.