Ubai Julaybib Benoitzon, 44, a Swedish citizen who has changed his legal name several times, had denied the charges against him, his lawyer Thomas Olsson said on Wednesday.
The court statement said the crimes included posing for pictures and video footage with dead or severely injured bodies while making victory signs and derogatory statements, with the aim of spreading the material as war propaganda online.
"The district court has assessed that the action constituted a serious violation of international humanitarian law," the statement said.
The court said it had not been able to definitively establish whether the bodies seen in the images were dead or alive.
The verdict said Ubai Julaybib Benoitzon, who has also been known as Bherlin Gildo and Nathan Benoitzon, at the time of the crimes was a member of a violent Islamist group, which it did not name.
The court sentenced Benoitzon, who had returned to Sweden, to four months in prison.
Olsson did not immediately reply to the question of whether his client would appeal the verdict.
The conflict in Syria, which spiralled out of an uprising against President Bashar al-Assad in 2011, has since killed more than 350,000 people, according to the United Nations.
(Reporting by Anna Ringstrom; editing by Phlippa Fletcher)
