Published Monday, 09 December 2013
A protest at City Hall last year following the vote on the flag. (© UTV)
Some unionist politicians raised concerns after it emerged that an old image of the building, which also included the big wheel, had been edited for the cards.
A spokesperson for the council said a current picture "should have been used".
He went on: "The photograph used is an older stock image and the only festive one we had that included both snow and the Christmas signage.
"The original also included the big wheel. It was an honest mistake to airbrush the photograph to reflect the current view of the City Hall.
"An authentic image of City Hall without the flag and big wheel should have been used. We have already apologised to the DUP leadership on the council and the explanation was accepted."
The council voted last year to change the flag-flying policy at City Hall to designated days, prompting widespread protests across Northern Ireland.
The cards, in their airbrushed format, have been printed and handed out to members of the council, who each get 50 to distribute as they please.
© UTV News