The Aquila
Aquila is the most famous type of Roman Standard and was a great symbol of power and pride. It was held by an experienced officer known as the Aquilifer. The Aquilifer's apparel consisted on a lion skin headdress. The Standard itself was of an eagle with its wings raised upwards surrounded by a laurel wreath. It was closely monitored and protected on and off the battlefield to ensure its safety from attack. Legions whose Aquila Standards were taken or had fallen in battle were considered a disgrace. This standard's power was shown during the time of Augustus, when he recovered a stolen Aquila Standard and then used that achievement to promote himself politically.
The Manus:
The Manus or open hand symbolized loyalty of the soldiers to their leaders and the trust they had in their guidance. The Standard itself was designed using multiple metal disk-like structures and topped with either a human hand or a spear-head shaped statue. The amount of disks on the Standard was thought to resemble the Century Unit number that Standard was a member of within the Cohort. Two belt-like leather tassels on either side or even a laurel wreath located on the Standard sometimes represented some type of honor or award won by that legion.
The Vexillum:
The Vexillum was unique from the other Standards, because it only had one flag-like banner, which was strictly used in the military and for signaling troops in battle. The Standard itself told which Legion or Cohort the Standard was a member of. The Standard also told the specific legionary or auxiliary units that did not serve in the main Legion or Cohort, which were called Vexillations. The unit type of of the Legion was typically written on the banner in Roman Numerals. The banner (usually red with tassels along the bottom edge) often had abbreviations of honorary titles or achievements or even pictures of animals that resembled positive Roman attributes. The boar and bull were commonly seen icons on the banners.
The Imago:
This Standard was only used in Imperial Legions. The Standard-bearer for this type of Legion was known as an Imaginifer. The standard itself included a metal portrait of an Emperor in power or who was responsible for the Legion's rise in power. The Imago was a reminder to the soldiers of the Roman people's and the Emperor's support to the them while fighting for their nation. The Standard itself could also have astrological significance representing the time the Legion was founded.
The Draco:
The Draco was carried by cavalry units and was the center of much Roman entertainment. The standard itself was made of a metal head of either a snake or dragon on top on a staff or pole. There was a piece of clothe attached to the head, like a train, that billowed in the wind as it was carried, making a hissing noise. The rider of the cavalry unit had the honor of carrying the Standard and he was known as the Draconarius. The Draco was a fairly new addition to the Standard, being only put to use in the Late Empire (250-400 A.D.). The soldiers played games with this Standard, such as one game consisting of soldiers winning points by using their javelins to hit the tail (piece of clothe) of the Standard.