Some 50 girls wearing headscarves are seen behind a Boko Haram militant who demands the release of fighters in return for freeing the girls.
The militant also says some of the girls have been killed in air strikes.
The group seized 276 final-year girls from a school in the northern town in April 2014.
It is believed to still be holding more than 200 of those kidnapped.
Non-Muslims were forcibly converted to Islam, and it is feared that many of the schoolgirls have been sexually abused and forced into "marriage" by their captors.