Tattoos that pay homage to the Norse cultures; Danish, Finnish, Icelandic, Norwegian, and Swedish ancestors are commonly referred to as "Viking" tattoos. This could realistically extend to the Aland Islands, the Faroe Islands, and Greenland, due to the nature of their founding as well. The Viking Era (793-1066 CE) was the age of discovery and travel for Scandinavians. This is, as most cultures and religions are, a pretty vast topic that is also obscured by alternate versions of stories, varying sources, the intentional and accidental misrepresentation by other cultures through clashing perspectives, and the destructive force of time upon an Aeon of oral traditions. There are written versions but the translations can be sketchy for the Eddas (Prose and Poetic, primarily stories of the Gods), while some of the Sagas (primarily stories of great achievements by people) have been kept pretty well intact. We will scratch the surface of these stories told by firelight here with the following elements:
Aegishjalmr- Only a few hundred years old; This symbol does not actually come from the Viking Era. The Helm of Awe (or Terror) is a symbol of protection. It is said that it can make one invisible, strike fear into one's enemies, or make the wearer impervious to attacks.
Freya- The Goddess of love
Gungnir- Odin's spear which can be thrown over the heads of his enemies to imbue them with fear.
Hlidskjalf- A large chair or throne from which all of the nine realms can be seen.
Horns of Kvasir (Triple Horn)- Three horns interwoven to represent the holders of the mead of poetry. The mead brewed from the truce born spittle man Kvasir's blood by two scheming dwarves. This representation is a bit newer, but still a great symbol of the story that represents Odin's cunning and the lengths that he will go to in order to gain knowledge and inspiration so well.
Odin- The King of the Aesir, he has a multitude of names which generally refer to different aspects of his psyche. He can be fierce and bloodthirsty. He cares not why people fight, just that they fight well. He is also a god of poetry and is often portrayed as a wise old man in a cloak with a wide brimmed hat and a walking stick. Odin has many facets as the all father. He is obsessed with knowledge and will do anything to attain it, including lying, cheating, and stealing. He sacrificed himself unto himself on a limb of Yggdrasil. Hanging upside down while wounded for nine nights to gain the power of the runes and traded one of his eyes to gain the sight from Mimir's well. He practices alchemy, enchantment, a touch of necromancy, and spellcraft. Like many of us he is also blinded by his lustful passions. There are many tales about him and his exploits.
Jormungandr- The great serpent and would be destroyer of Midgard (Earth). This sea wyrm is said to battle with Thor during Ragnarok. It is said when Jormundgandr shrugs we get earthquakes and tidal waves.
Loki- God of trickery, Loki loves to point out the flaws of others and only keeps peoples secrets if it suits his purpose. Otherwise he will fervently use their secrets against them.
Mjolnir- Thor's hammer is a fairly recognizable symbol to those interested in Viking lore. Many different types of these for necklaces have been found during excavations. It is said to have developed as a symbol in opposition to the Christian cross that could still be worn without raising too many suspicions due to the handle resembling a cross, but we have found no solid evidence of this yet.
Thor- The God of thunder is a scrapping brute that beats on giants for fun. Quick to temper but loyal to a fault he would quite often take on the role of protector or enforcer for the Aesir. He has a chariot pulled by two goats that he can eat every night and resurrect every day with Mjolnir, as long as their bones are not broken.
Runes- Ancient lettering generally inscribed on stones for learning about the future, past, and present. In the lore they were given to Odin, in reality the runes evolved and migrated throughout Europe over long periods of time. It is very important to know what rune set you are referencing since there are so many. A very common mistake being made these days is the confusion of Gothic runes with Norse runes. They have many visual similarities but the meanings are drastically different. Each rune has a meaning and it's position may invert it's symbolism. They are read right to left in older times but eventually began to be read in many different directions. Some of the meanings have been altered by more modern readers as well in order to be more socially acceptable, because if you don't like history you just change it right, smh?
Valknut- Currently a symbol of Odinists and followers of Asatru. It is said to symbolize the nine worlds, nine days Odin hung from Yggdrasil, where he learned 9 powerful songs, and the secret of the runes. Modern archaeology has pointed at it also being a symbol used heavily by "death cults" during the Viking era.
Vegvisir- The Viking Compass. A younger symbol like the Aegishjalmr, this is an Icelandic magical stave that is said to keep you from getting lost in dense fog. In more modern times it is used to represent staying the course and not losing your direction.
Yggdrasil- This is the tree in which the nine realms and many other creatures exist. Though the nine realms are named nowhere does any lore state that they are the only realms and sometimes the realms change from source to source. It is essentially the tree of life since all existence is said to be within it's embrace. This is not to be confused with the Celtic Tree of Life that represents the cycle of nature, but is commonly intertwined anyway because humans are just that way.