Symbols - Some of which were used on the secrets - and with various meanings
SCROLLING RIBBON, called an Escroll or Scroll, which looks like a scrolling banner, OR A LONG SCROLL WHERE UPON THE WRITING OF HISTORY TAKES PLACE.
Medieval use of the WHEEL - see secret #70 for more uses of the wheel.
At left is the wheel that was used on many of the image secrets.

Also, see the MOON cycle illustration below on page.

Note: In heraldry, the wagon wheel is symbolic of transportation, successful journeys and expeditions, and also perpetuity.
Then again, the wheel in Nostradamus' images could represent 'Catherine's breaking Wheel', which was used extensively by the Church during their long history of torture and murder, as depicted in the photo below right - click on image to view larger version.The breaking wheel (also known as the Catherine wheel because she was torture upon this type of wheel), was a torturous capital punishment device used for public execution.The breaking wheel was a great dishonor, rather like crucifixion in Antiquity.
The History Channel reported that the wheel on the secrets [as above] represented the Alchemy Wheel - see example at right. OR, it could be a continuation of an ancient wheel found in Sumer and Babylon such as this one.

CHAPLET: A circular garland, usually woven of 4 flowers (equally spaced), leaves, and foliage, that traditionally indicated honour or celebration.  The wreath in ancient Egypt was most popular in the form of a chaplet made by sewing flowers to linen bands and tying them around the head.  In ancient Greece, wreaths, usually made of olive, pine, laurel, celery, or palm, were awarded to athletes victorious in the Olympic games and as prizes to poets and orators.  In Rome, laurel crowns were bestowed as a mark of honour, especially on civil officials and returning warriors.  The heraldic chaplet is a crown of joy and admiration, honour and celebration. In the Catholic Church, the chaplet was a devotional prayer headdress.
SEE secret #72 FOR MORE ON THE CHAPLET
BUCK (STAG): The Stag is the male deer indicative of long life (fabled to live over 1000 years). The Stag is a symbol of wisdom, regeneration, growth, and virility. Because its antlers resemble branches, the Stag has been associated with the 'Tree of Life' and because of the way it renews its antlers, it is used as a symbol of regeneration. During the Middle Ages, the Stag was often shown with a crucifix between its horns where, in Christianity, it represented purity and solitude and was the enemy of Satan, the serpent. The Celts believed the Stag guided souls through the darkness (the world for departed souls). In Greco-Roman mythology it was an animal sacred to Artemis. Heraldic writers say of the Stag: "One who will not fight unless provoked, a lover of music and harmony who well foresees his times and opportunities". The Vikings used the stag as a symbol of royal status and the Romans used it as an icon of masculine values.
SCORPION: The Scorpion is the symbol of both wisdom and self-destruction. The Scorpion's sting could also be directed at enemies and so amulets in the form of Scorpions were worn in many cultures as a protection against evil.  It was thought that the Scorpion produced both venom and anti-venom.  In some areas this made it an emblem of resurrection and constancy. Selket, the Egyptian goddess and protectress of the dead had the head of a scorpion.
Fire: Ancient symbol of a ruler; also symbolizes the transforming energy of the Holy Spirit's actions; denotes zeal; was anciently connected with the universal worship of the sun. However, fire can indicate the demise of someone or something.
Eradicated treesTorn up by the roots. Eradicated, which means eliminated, utterly destroyed, yanked out of the ground, roots and all.
MOON - In Astrological terms, the moon represents the MOTHER, the 4th house, domestic, real estate, home life, beginning of life, nurturing, and women.
Crescent. In Heraldry, a half-moon with the horns turned upwards.
When used as a mark of cadency it denotes the second son. If the horns are turned towards the dexter, it is termed an increscent. If the horns are to the sinister, a decrescent.  When the horns are turned down it is termed a crescent reversed. Decrescent. The half-moon looking to the sinister. [Sinister - the left. i.e. the right to the spectator. Dexter -the right hand side i.e. left to the spectator.]
STARS: Estoile.  A star of six waved points.  When the estoile has more than six points, the number should be expressed.  When of eight or more points half should be straight and half waved. ESTOILE: Celestial goodness, a man of noble personage.  A STAR ON A SHIELD INDICATES AN ENSIGN OF KNIGHTLY RANK, common in the Heraldry of all nations.
Fleur-de-lis: Heraldically this was a flower, it stands at the head of the flowers in heraldry. Its origin is unknown; one "authority" claiming that it was brought down from heaven by an angel for the arms of France.  It is also said to mean the flower of Louis (Fleur de Louis), and was certainly used by Louis VII. It is undoubtedly the "flower of the Lilly." Originally the royal banner of France was semee-of-lis (completely covered with fleurs-de-lis); but from the time of Charles VI it has consisted of three golden fleurs-de-lis on a blue field.  The fleurs-de-lis did not at first meet with much favor in England so it did not become popular, in fact, until its assumption by Edward III.  George VI, on his accession, abolished French quartering, in the English royal arms. When used as a difference the fleur-de-lis represents the sixth son. Note: France represents the tribe of Reuben, so the original flower may have been Mandrakes.
CASTLE (tower, chateau): The emblem of grandeur and society, and has been granted sometimes to one who has faithfully held one for his king, or who has captured one by force or strategy. The castle of Western Europe was a Norman creation, stemming from the 10th and 11th-century 'Norman Mound' castles.  A castle that became the model for many English and Norman castles was the formidable castle built at Arques in Normandy by Henry I of England.  In the Middle East the Crusaders developed great castles with double circuits of curving outer walls and towers or turrets to overlook all sections of the wall.  Early in the 13th century the medieval castle, a mixture of Norman, English, and Byzantine elements was born. A Castle, the emblem of safety.
Fire in the towers: Ancient symbol of a firy rule; also can symbolize the transforming energy of the Holy Spirit's actions.
  For instance: King Louis VI (1108-1137) - to revive French royal power was recounted by his minister, Abbot Suger. None could behold the castle tower flaming like the fires of hell and not exclaim, "The whole universe will fight for him against these madmen." Those are they who, when thou didst issue commands to destroy the commune of Laon, did burn with fire not only the city of Laon; but the noble church of the Mother of God, and many others beside. What I believe the images are saying with the tower in flames is that the 'Church of Rome' would see its end, perhaps predicting the end to the Holy Roman Empire - not visualizing 2012 events.


RETURN
Many Vatican images were found at the website of: http://schulen.eduhi.at/stift_kremsmuenster/vat/index.htm
Sources:
Thanks to: http://en.wikipedia.org/, and the Catholic Encyclopedia for much information gathered to make up this interpretation.