This cartoon by Chappatte from Le Temps, Geneva shows Saint Peter at the gates of heaven. Attached to the railings behind is a picture of him with a smiling Nelson Mandela, who has signed the picture.
Nelson Mandela has died and gone to heaven. We are meant to assume that since Mandela was such a special person, Saint Peter wanted to have a souvenir photograph taken with him, just like members of the public do with celebrities.
In art (and cartoons), St Peter is usually depicted as a white-haired, bearded man in a blue robe, often holding a key or keys, which refer to Matthew 16:19. Following on from this, many paintings and literary accounts of Heaven show him stationed at the gate. There are traditionally two keys, one gold and one silver, representing the two conditions necessary for salvation: the silver key represents repentance, which comes from the person concerned; and the gold key represents forgiveness, which comes from God. [source: Conservapedia]